{"segment":[{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[4]],"list":[{"point":5,"ques":"Trong c\u00e1c h\u00ecnh v\u1ebd sau, h\u00ecnh v\u1ebd n\u00e0o bi\u1ec3u di\u1ec5n m\u1ed9t h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng.<br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/H8_B21_D1.1.png' \/><\/center>","select":["A. H\u00ecnh 1, H\u00ecnh 3 v\u00e0 H\u00ecnh 4","B. H\u00ecnh 1, H\u00ecnh 3 v\u00e0 H\u00ecnh 6","C. H\u00ecnh 1, H\u00ecnh 2 v\u00e0 H\u00ecnh 3","D. H\u00ecnh 1, H\u00ecnh 2 v\u00e0 H\u00ecnh 4"],"hint":"D\u1ef1a v\u00e0o \u0111\u1ecbnh ngh\u0129a h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng","explain":" <span class='basic_left'>H\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u00e0 h\u00ecnh g\u1ed3m hai m\u1eb7t \u0111\u00e1y l\u00e0 c\u00e1c \u0111a gi\u00e1c song song v\u1edbi nhau v\u00e0 c\u00e1c m\u1eb7t b\u00ean l\u00e0 c\u00e1c h\u00ecnh ch\u1eef nh\u1eadt.<br\/>- H\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt, h\u00ecnh l\u1eadp ph\u01b0\u01a1ng l\u00e0 c\u00e1c h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng t\u1ee9 gi\u00e1c.<br\/>- H\u00ecnh 4 c\u00f3 hai \u0111\u00e1y l\u00e0 hai tam gi\u00e1c n\u00ean \u0111\u01b0\u1ee3c g\u1ecdi l\u00e0 h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng tam gi\u00e1c.<br\/>C\u00e1c h\u00ecnh bi\u1ec3u di\u1ec5n m\u1ed9t h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u00e0 H\u00ecnh 1, H\u00ecnh 2 v\u00e0 H\u00ecnh 4<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 D<\/span><\/span>","column":2}]}],"id_ques":1840},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":5,"ques":"C\u00e1c m\u1eb7t b\u00ean c\u1ee7a h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u00e0 h\u00ecnh g\u00ec?","select":["A. H\u00ecnh b\u00ecnh h\u00e0nh","B. H\u00ecnh thoi","C. H\u00ecnh ch\u1eef nh\u1eadt","D. H\u00ecnh vu\u00f4ng"],"hint":"D\u1ef1a v\u00e0o \u0111\u1ecbnh ngh\u0129a h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng","explain":" <span class='basic_left'>C\u00e1c m\u1eb7t b\u00ean c\u1ee7a h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u00e0 h\u00ecnh ch\u1eef nh\u1eadt<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 C<\/span><\/span>","column":2}]}],"id_ques":1841},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":5,"ques":"M\u1ed9t h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng c\u00f3 \u0111\u00e1y l\u00e0 ng\u0169 gi\u00e1c th\u00ec h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng \u0111\u00f3 c\u00f3:<br\/>","select":["A. $7$ m\u1eb7t, $15$ c\u1ea1nh, $10$ \u0111\u1ec9nh.","B. $7$ m\u1eb7t, $10$ c\u1ea1nh, $10$ \u0111\u1ec9nh.","C. $5$ m\u1eb7t, $15$ c\u1ea1nh, $10$ \u0111\u1ec9nh.","D. $5$ m\u1eb7t, $10$ c\u1ea1nh, $10$ \u0111\u1ec9nh."],"hint":"","explain":" <span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/H8_B21_D1.10.png' \/><\/center><br\/>h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng c\u00f3 \u0111\u00e1y l\u00e0 ng\u0169 gi\u00e1c c\u00f3 $7$ m\u1eb7t, $15$ c\u1ea1nh, $10$ \u0111\u1ec9nh.<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 A<\/span><br\/><span class='basic_green'>Ghi nh\u1edb:<\/span> Trong h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng , lu\u00f4n c\u00f3:<br\/>- S\u1ed1 m\u1eb7t $=$ S\u1ed1 c\u1ea1nh \u1edf \u0111\u00e1y $+ 2$<br\/>- S\u1ed1 c\u1ea1nh $= 3 *$ S\u1ed1 c\u1ea1nh \u1edf \u0111\u00e1y<br\/>- S\u1ed1 \u0111\u1ec9nh $= 2 *$ S\u1ed1 c\u1ea1nh \u1edf \u0111\u00e1y<br\/>- S\u1ed1 m\u1eb7t $+$ S\u1ed1 \u0111\u1ec9nh $-$ S\u1ed1 c\u1ea1nh $=2$ <\/span>","column":2}]}],"id_ques":1842},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["8"],["6"],["12"],["10"],["7"],["15"]]],"list":[{"point":5,"width":50,"type_input":"","ques":"Cho h\u00ecnh v\u1ebd: <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/H8_B21_D1.14.png' \/><\/center><br\/><table><tr><th><\/th><th>S\u1ed1 c\u1ea1nh m\u1ed9t \u0111\u00e1y<\/th><th>S\u1ed1 \u0111\u1ec9nh<\/th><th>S\u1ed1 m\u1eb7t<\/th><th>S\u1ed1 c\u1ea1nh<\/th><\/tr><tr><td>H\u00ecnh 1<\/td><td>$4$<\/td><td>_input_<\/td><td>_input_<\/td><td>_input_<\/td><\/tr><tr><td>H\u00ecnh 2<\/td><td>$5$<\/td><td>_input_<\/td><td>_input_<\/td><td>_input_<\/td><\/tr><\/table>","hint":"","explain":"<span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/H8_B21_D1.14.png' \/><\/center><br\/><table><tr><th><\/th><th>S\u1ed1 c\u1ea1nh m\u1ed9t \u0111\u00e1y<\/th><th>S\u1ed1 \u0111\u1ec9nh<\/th><th>S\u1ed1 m\u1eb7t<\/th><th>S\u1ed1 c\u1ea1nh<\/th><\/tr><tr><td>H\u00ecnh 1<\/td><td>$4$<\/td><td>$8$<\/td><td>$6$<\/td><td>$12$<\/td><\/tr><tr><td>H\u00ecnh 2<\/td><td>$5$<\/td><td>$10$<\/td><td>$7$<\/td><td>$15$<\/td><\/tr><\/table><br\/><span class='basic_pink'>V\u1eady c\u00e1c s\u1ed1 ph\u1ea3i \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $8;6;12;10;7$ v\u00e0 $15$<\/span><br\/><span class='basic_green'>Ghi nh\u1edb:<\/span>Trong h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng , lu\u00f4n c\u00f3: <br\/>- S\u1ed1 m\u1eb7t = S\u1ed1 c\u1ea1nh \u1edf \u0111\u00e1y + 2<br\/>- S\u1ed1 c\u1ea1nh = 3 * S\u1ed1 c\u1ea1nh \u1edf \u0111\u00e1y<br\/>- S\u1ed1 \u0111\u1ec9nh = 2 * S\u1ed1 c\u1ea1nh \u1edf \u0111\u00e1y<br\/>- S\u1ed1 m\u1eb7t +S\u1ed1 \u0111\u00e1y-S\u1ed1 c\u1ea1nh =2 <\/span>"}]}],"id_ques":1843},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0110\u00fang ho\u1eb7c Sai","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":5,"ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/12.jpg' \/><\/center>M\u1ed9t h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng c\u00f3 $6$ m\u1eb7t th\u00ec h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng \u0111\u00f3 l\u00e0 h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng t\u1ee9 gi\u00e1c. <b>\u0110\u00fang<\/b> hay <b>Sai<\/b>.","select":["\u0110\u00fang","Sai"],"hint":"T\u00ecm s\u1ed1 c\u1ea1nh \u1edf \u0111\u00e1y.","explain":" <span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/H8_B21_D1.17.png' \/><\/center>M\u1ed9t h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng c\u00f3 $6$ m\u1eb7t th\u00ec c\u00f3 $4$ c\u1ea1nh \u1edf \u0111\u00e1y.<br\/>N\u00ean h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng \u0111\u00f3 l\u00e0 h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng t\u1ee9 gi\u00e1c.<br\/><span class='basic_pink'>V\u1eady kh\u1eb3ng \u0111\u1ecbnh tr\u00ean l\u00e0 \u0110\u00fang<\/span><\/span>","column":2}]}],"id_ques":1844},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0110\u00fang ho\u1eb7c Sai","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":5,"ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/16.jpg' \/><\/center>C\u00f3 t\u1ed3n t\u1ea1i m\u1ed9t h\u00ecnh l\u1eb1ng tr\u1ee5 \u0111\u1ee9ng $25$ \u0111\u1ec9nh kh\u00f4ng?","select":["C\u00f3","Kh\u00f4ng"],"hint":"Xem m\u1ed1i li\u00ean h\u1ec7 gi\u1eefa s\u1ed1 \u0111\u1ec9nh v\u00e0 s\u1ed1 c\u1ea1nh c\u1ee7a \u0111a gi\u00e1c \u1edf \u0111\u00e1y","explain":" <span class='basic_left'>G\u1ecdi s\u1ed1 c\u1ea1nh c\u1ee7a \u0111a gi\u00e1c \u1edf \u0111\u00e1y l\u00e0 $n$ ($n\\in\\mathbb {N^*},\\,n\\ge 3$)<br\/>Khi \u0111\u00f3 s\u1ed1 \u0111\u1ec9nh c\u1ee7a h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u00e0 $2n$ l\u00e0 m\u1ed9t s\u1ed1 ch\u1eb5n.<br\/> N\u00ean kh\u00f4ng th\u1ec3 l\u00e0m \u0111\u01b0\u1ee3c m\u1ed9t h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng c\u00f3 $25$ \u0111\u1ec9nh.<br\/><span class='basic_pink'>C\u00e2u tr\u1ea3 l\u1eddi l\u00e0 kh\u00f4ng.<\/span><\/span>","column":2}]}],"id_ques":1845},{"time":24,"part":[{"title":"Ch\u1ecdn <u>nh\u1eefng<\/u> \u0111\u00e1p \u00e1n \u0111\u00fang","title_trans":"Ch\u1ecdn \u0111\u01b0\u1ee3c nhi\u1ec1u \u0111\u00e1p \u00e1n","temp":"checkbox","correct":[["2","4","5"]],"list":[{"point":10,"img":"","ques":"Trong c\u00e1c s\u1ed1 sau, s\u1ed1 n\u00e0o c\u00f3 th\u1ec3 l\u00e0 s\u1ed1 c\u1ea1nh c\u1ee7a m\u1ed9t h\u00ecnh l\u0103ng tr\u1ee5?","hint":"Xem m\u1ed1i li\u00ean h\u1ec7 gi\u1eefa s\u1ed1 c\u1ea1nh c\u1ee7a h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng v\u00e0 s\u1ed1 c\u1ea1nh c\u1ee7a \u0111a gi\u00e1c \u1edf \u0111\u00e1y ","column":2,"number_true":2,"select":["A. $13$","B. $12$","C. $26$","D. $24$","E. $54$","F. $28$"],"explain":" <span class='basic_left'>G\u1ecdi s\u1ed1 c\u1ea1nh c\u1ee7a \u0111a gi\u00e1c \u1edf \u0111\u00e1y l\u00e0 $n$ ($n\\in\\mathbb {N^*},\\,n\\ge 3$)<br\/>Khi \u0111\u00f3 s\u1ed1 c\u1ea1nh c\u1ee7a h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u00e0 $3n$ l\u00e0 m\u1ed9t s\u1ed1 chia h\u1ebft cho $3$. N\u00ean c\u00e1c s\u1ed1 c\u00f3 th\u1ec3 l\u00e0 s\u1ed1 c\u1ea1nh c\u1ee7a m\u1ed9t h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u00e0: $12;\\,24;\\,54$<br\/>V\u1edbi s\u1ed1 c\u1ea1nh l\u00e0 $12$, suy ra s\u1ed1 c\u1ea1nh c\u1ee7a \u0111a gi\u00e1c \u1edf \u0111\u00e1y l\u00e0 $4$<br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/H8_B21_D1.17.png' \/><\/center><br\/>V\u1edbi s\u1ed1 c\u1ea1nh l\u00e0 $24$, suy ra s\u1ed1 c\u1ea1nh c\u1ee7a \u0111a gi\u00e1c \u1edf \u0111\u00e1y l\u00e0 $8$<br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/H8_B21_D1.18.png' \/><\/center><br\/>V\u1edbi s\u1ed1 c\u1ea1nh l\u00e0 $54$, suy ra s\u1ed1 c\u1ea1nh c\u1ee7a \u0111a gi\u00e1c \u1edf \u0111\u00e1y l\u00e0 $18$<br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/H8_B21_D1.19.png' \/><\/center><br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 B,D v\u00e0 E<\/span><br\/><\/span>"}]}],"id_ques":1846},{"time":24,"part":[{"title":"Ch\u1ecdn <u>nh\u1eefng<\/u> \u0111\u00e1p \u00e1n \u0111\u00fang","title_trans":"Ch\u1ecdn \u0111\u01b0\u1ee3c nhi\u1ec1u \u0111\u00e1p \u00e1n","temp":"checkbox","correct":[["1","2","4","5"]],"list":[{"point":10,"img":"","ques":"Cho h\u00ecnh v\u1ebd.<br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/H8_B21_D1.2.png' \/><\/center> C\u00e1c kh\u1eb3ng \u0111\u1ecbnh sau, kh\u1eb3ng \u0111\u1ecbnh n\u00e0o \u0111\u00fang?","hint":"","column":1,"number_true":2,"select":["A. $AA'\/\/BB'$","B. $A'B'\\bot B'B$","C. $mp(A'B'BA) \\bot mp(BB'C'C)$","D. $mp(ABC)\/\/mp(A'B'C')$","E. $AA' \\bot mp(ABC)$","F. $mp(A'B'BA) \/\/ mp(A'C'CA)$"],"explain":"<span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/H8_B21_D1.2.png' \/><\/center><br\/>A. \u0110\u00fang v\u00ec $A'B'BA$ l\u00e0 h\u00ecnh ch\u1eef nh\u1eadt n\u00ean $AA'\/\/BB'$<br\/>B. \u0110\u00fang v\u00ec $A'B'BA$ l\u00e0 h\u00ecnh ch\u1eef nh\u1eadt n\u00ean $A'B'\\bot B'B$<br\/>C. Sai v\u00ec $BC$ kh\u00f4ng vu\u00f4ng g\u00f3c v\u1edbi $AB$. <br\/>M\u1eb7t ph\u1eb3ng $(P)$ vu\u00f4ng g\u00f3c v\u1edbi m\u1eb7t ph\u1eb3ng $(Q)$ khi t\u1ed3n t\u1ea1i $a\\in mp(P)$ v\u00e0 $a\\bot mp(Q)$<br\/>D. \u0110\u00fang v\u00ec $A'B'\/\/AB$.<br\/>M\u1eb7t ph\u1eb3ng $mp(P) \/\/mp(Q)$ khi t\u1ed3n t\u1ea1i $a\\in mp(P)$ v\u00e0 $a\/\/ mp(Q)$<br\/>E. \u0110\u00fang v\u00ec $AA'\\bot AC$ v\u00e0 $AA'\\bot AB$ n\u00ean $A'A \\bot mp(ABC)$<br\/>F. Sai v\u00ec hai m\u1eb7t ph\u1eb3ng giao nhau b\u1edfi \u0111\u01b0\u1eddng th\u1eb3ng $AA'$<br\/><span class='basic_pink'>C\u00e1c kh\u1eb3ng \u0111\u1ecbnh \u0111\u00fang l\u00e0 A, B, D v\u00e0 E.<\/span><br\/><b>Ghi nh\u1edb:<\/b> Trong h\u00ecnh h\u1ecdc kh\u00f4ng gian:<br\/>- N\u1ebfu m\u1ed9t \u0111\u01b0\u1eddng th\u1eb3ng vu\u00f4ng g\u00f3c v\u1edbi hai \u0111\u01b0\u1eddng th\u1eb3ng c\u1eaft nhau c\u00f9ng thu\u1ed9c m\u1ed9t m\u1eb7t ph\u1eb3ng th\u00ec \u0111\u01b0\u1eddng th\u1eb3ng \u0111\u00f3 vu\u00f4ng g\u00f3c v\u1edbi m\u1eb7t ph\u1eb3ng. T\u1ee9c l\u00e0:<br\/>$\\left\\{ \\begin{align} & a\\bot b \\\\ & a\\bot c \\\\ & b,c\\in (P) \\\\ \\end{align} \\right.\\Rightarrow a\\bot (P) $<br\/>- N\u1ebfu m\u1ed9t \u0111\u01b0\u1eddng th\u1eb3ng vu\u00f4ng g\u00f3c v\u1edbi m\u1ed9t m\u1eb7t ph\u1eb3ng th\u00ec n\u00f3 vu\u00f4ng g\u00f3c v\u1edbi m\u1ecdi \u0111\u01b0\u1eddng th\u1eb3ng n\u1eb1m trong m\u1eb7t ph\u1eb3ng. T\u1ee9c l\u00e0: $\\left\\{ \\begin{align} & a\\bot (P) \\\\ & b\\in (P) \\\\ \\end{align} \\right.\\Rightarrow a\\bot b$. <br\/><\/span>"}]}],"id_ques":1847},{"time":24,"part":[{"time":3,"title":"N\u1ed1i hai m\u1eb7t ph\u1eb3ng song song v\u1edbi nhau ","title_trans":"","audio":"","temp":"matching","correct":[["3","1","4","2"]],"list":[{"point":5,"image":"https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/H8_B21_D1.15.png","left":["$mp(ABCDEF)$ ","$mp(A'B'BA)$","$mp(D'C'CD)$ ","$mp(B'C'CB)$"],"right":["$mp(E'D'DE)$","$mp(E'F'FE)$","$mp(A'B'C'D'E'F')$","$mp(A'F'FA)$"],"top":100,"hint":"","explain":"<span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/H8_B21_D1.15.png' \/><\/center>h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng tr\u00ean l\u00e0 h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u1ee5c gi\u00e1c \u0111\u1ec1u n\u00ean hai m\u1eb7t \u0111\u1ed1i di\u1ec7n th\u00ec song song v\u1edbi nhau. <br\/>(<i> h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u1ee5c gi\u00e1c \u0111\u1ec1u l\u00e0 h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng c\u00f3 \u0111\u00e1y l\u00e0 l\u1ee5c gi\u00e1c \u0111\u1ec1u<\/i>)<br\/>Khi \u0111\u00f3, ta c\u00f3:<br\/>- $mp(ABCDEF)\/\/mp(A'B'C'D'E'F')$<br\/>- $mp(A'B'BA)\/\/mp(E'D'DE)$<br\/>- $mp(D'C'CD)\/\/mp(A'F'FA)$<br\/>- $mp(B'C'CB)\/\/mp(E'F'FE)$<\/span>"}]}],"id_ques":1848},{"time":2,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["2ph","2p.h","2.p.h","h2p","h.2p","h.2.p","2hp"],["Sh","S.h","hS","h.S"]]],"list":[{"point":5,"width":50,"type_input":"","ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/8.jpg' \/><\/center><span class='basic_left'>Cho h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng c\u00f3 chi\u1ec1u cao l\u00e0 $h$ (\u0111\u01a1n v\u1ecb \u0111\u1ed9 d\u00e0i). \u0110\u00e1y l\u00e0 \u0111a gi\u00e1c c\u00f3 chu vi l\u00e0 $2p$ (\u0111\u01a1n v\u1ecb \u0111\u1ed9 d\u00e0i) v\u00e0 di\u1ec7n t\u00edch l\u00e0 $S$ (\u0111\u01a1n v\u1ecb di\u1ec7n t\u00edch).<br\/>C\u00f4ng th\u1ee9c t\u00ednh di\u1ec7n t\u00edch xung quanh c\u1ee7a h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u00e0 $S_{xq}=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}$ (\u0111\u01a1n v\u1ecb di\u1ec7n t\u00edch)<br\/>Th\u1ec3 t\u00edch c\u1ee7a h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u00e0 $V=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}$(\u0111\u01a1n v\u1ecb th\u1ec3 t\u00edch)<\/span>","hint":"","explain":"<span class='basic_left'>Cho h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng c\u00f3 chi\u1ec1u cao l\u00e0 $h\\,$ (\u0111\u01a1n v\u1ecb \u0111\u1ed9 d\u00e0i). \u0110\u00e1y l\u00e0 \u0111a gi\u00e1c c\u00f3 chu vi l\u00e0 $2p\\,$ (\u0111\u01a1n v\u1ecb \u0111\u1ed9 d\u00e0i) v\u00e0 di\u1ec7n t\u00edch l\u00e0 $S$ (\u0111\u01a1n v\u1ecb \u0111\u1ed9 d\u00e0i).<br\/>C\u00f4ng th\u1ee9c t\u00ednh di\u1ec7n t\u00edch xung quanh c\u1ee7a h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u00e0 t\u1ed5ng di\u1ec7n t\u00edch c\u00e1c m\u1eb7t b\u00ean c\u1ee7a h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng v\u00e0 b\u1eb1ng chu vi \u0111\u00e1y nh\u00e2n chi\u1ec1u cao n\u00ean $S_{xq}=2ph$ (\u0111\u01a1n v\u1ecb di\u1ec7n t\u00edch)<br\/>Th\u1ec3 t\u00edch c\u1ee7a h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng b\u1eb1ng di\u1ec7n t\u00edch \u0111\u00e1y nh\u00e2n chi\u1ec1u cao n\u00ean $V=S.h$ (\u0111\u01a1n v\u1ecb th\u1ec3 t\u00edch)<\/span>"}]}],"id_ques":1849},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["675"],["2250"]]],"list":[{"point":5,"width":50,"type_input":"","ques":"Cho h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng ng\u0169 gi\u00e1c c\u00f3 c\u00e1c k\u00edch th\u01b0\u1edbc nh\u01b0 h\u00ecnh v\u1ebd: <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/H8_B21_D1.20.png' \/><\/center><br\/>Di\u1ec7n t\u00edch xung quanh c\u1ee7a h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u00e0 $\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}\\,(cm^2)$<br\/>Th\u1ec3 t\u00ednh h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u00e0 $\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}(cm^3)$","hint":"\u00c1p d\u1ee5ng c\u00f4ng th\u1ee9c t\u00ednh di\u1ec7n t\u00edch xung quanh v\u00e0 th\u1ec3 t\u00edch h\u00ecnh l\u0103ng tr\u1ee5.","explain":"<span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/H8_B21_D1.20.png' \/><\/center><br\/>Di\u1ec7n t\u00edch xung quanh c\u1ee7a h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u00e0 $S_{xq}=45.15=675\\,(cm^2)$<br\/>Th\u1ec3 t\u00ednh h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u00e0 $V=150.15=2250\\,(cm^3)$<br\/><span class='basic_pink'>V\u1eady c\u00e1c s\u1ed1 ph\u1ea3i \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $675$ v\u00e0 $2250$.<\/span><\/span>"}]}],"id_ques":1850},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":5,"ques":"T\u00ednh di\u1ec7n t\u00edch to\u00e0n ph\u1ea7n c\u1ee7a cu\u1ed1n l\u1ecbch \u0111\u1ec3 b\u00e0n h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng tam gi\u00e1c, k\u00edch th\u01b0\u1edbc nh\u01b0 h\u00ecnh v\u1ebd. <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/H8_B21_D1.4.png' \/><\/center>","select":["A. $2170\\,cm^2$","B. $2410\\,cm^2$","C. $240\\,cm^2$","D. $4210\\,cm^2$"],"hint":"Di\u1ec7n t\u00edch to\u00e0n ph\u1ea7n b\u1eb1ng di\u1ec7n t\u00edch xung quanh + Di\u1ec7n t\u00edch hai \u0111\u00e1y.","explain":" <span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/H8_B21_D1.4.png' \/><\/center>Chu vi \u0111\u00e1y l\u00e0 $2p=25+25+12=62\\,(cm)$<br\/>Di\u1ec7n t\u00edch xung quanh l\u00e0 $S_{xq}=62.35=2170\\,(cm^2)$<br\/>Di\u1ec7n t\u00edch m\u1ed7i \u0111\u00e1y l\u00e0 $S_{\u0111\u00e1y}=\\dfrac{1}{2}.12.20=120\\,(cm^2)$<br\/>Di\u1ec7n t\u00edch to\u00e0n ph\u1ea7n l\u00e0 $S_{tp}=2170+120.2=2410\\,(cm^2)$<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 B <\/span><\/span>","column":2}]}],"id_ques":1851},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[4]],"list":[{"point":5,"ques":"T\u00ednh di\u1ec7n t\u00edch gi\u1ea5y b\u00f3ng k\u00ednh c\u1ea7n d\u00e1n xung quanh \u0111\u1ec3 ho\u00e0n thi\u1ec7n chi\u1ebfc \u0111\u00e8n l\u1ed3ng h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u1ee5c gi\u00e1c \u0111\u1ec1u c\u00f3 c\u1ea1nh d\u00e0i $15\\,cm$ v\u00e0 cao $35\\,cm$ <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/H8_B21_D1.5.png' \/><\/center><br\/>(<i>h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u1ee5c gi\u00e1c \u0111\u1ec1u l\u00e0 h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng c\u00f3 \u0111\u00e1y l\u00e0 l\u1ee5c gi\u00e1c \u0111\u1ec1u.<\/i>)","select":["A. $2100\\,cm^2$","B. $3600\\,cm^2$","C. $1050\\,cm^2$","D. $3150\\,cm^2$"],"hint":"Di\u1ec7n t\u00edch gi\u1ea5y b\u00f3ng k\u00ednh b\u1eb1ng di\u1ec7n t\u00edch xung quanh c\u1ee7a h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng.","explain":" <span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/H8_B21_D1.11.png' \/><\/center>Chu vi \u0111\u00e1y l\u00e0 $2p=15.6=90\\,(cm)$<br\/>Di\u1ec7n t\u00edch xung quanh l\u00e0 $S_{xq}=90.35=3150\\,(cm^2)$<br\/>V\u1eady c\u1ea7n $3150 cm^2$ gi\u1ea5y b\u00f3ng k\u00ednh \u0111\u1ec3 d\u00e1n ho\u00e0n thi\u1ec7n chi\u1ebfc \u0111\u00e8n l\u1ed3ng.<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 D <\/span><\/span>","column":2}]}],"id_ques":1852},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["240"]]],"list":[{"point":5,"width":50,"type_input":"","ques":"T\u00ednh th\u1ec3 t\u00edch h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng c\u00f3 chi\u1ec1u cao $10 cm$, \u0111\u00e1y l\u00e0 tam gi\u00e1c c\u00f3 $3$ c\u1ea1nh l\u1ea7n l\u01b0\u1ee3t b\u1eb1ng $6 cm,\\, 8 cm$ v\u00e0 $10 cm$<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/H8_B21_D1.21.png' \/><\/center><br\/><b> \u0110\u00e1p s\u1ed1: <\/b> _input_ ($cm^3$)","hint":"\u0110\u00e1y l\u00e0 tam gi\u00e1c g\u00ec?","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/><b>B\u01b0\u1edbc 1:<\/b> Ch\u1ee9ng minh \u0111\u00e1y l\u00e0 tam gi\u00e1c vu\u00f4ng<br\/> <b>B\u01b0\u1edbc 2: <\/b> T\u00ednh di\u1ec7n t\u00edch \u0111\u00e1y.<br\/><b>B\u01b0\u1edbc 3:<\/b> T\u00ednh th\u1ec3 t\u00edch h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng <br\/><span class='basic_green'>B\u00e0i gi\u1ea3i<\/span><br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/H8_B21_D1.21.png' \/><\/center><br\/>Ta c\u00f3, h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng c\u00f3 \u0111\u00e1y l\u00e0 tam gi\u00e1c c\u00f3 3 c\u1ea1nh l\u00e0 $6\\,cm;\\,8\\,cm$ v\u00e0 $10\\,cm$<br\/>V\u00ec $6^2+8^2=36+64=100=10^2$ <br\/>V\u1eady theo \u0111\u1ecbnh l\u00fd Pytago \u0111\u1ea3o, tam gi\u00e1c \u1edf \u0111\u00e1y c\u1ee7a h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u00e0 tam gi\u00e1c vu\u00f4ng.<br\/>Di\u1ec7n t\u00edch \u0111\u00e1y l\u00e0 $\\dfrac{1}{2}.6.8=24\\,(cm^2)$<br\/>Th\u1ec3 t\u00edch h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u00e0 $24.10=240\\,(cm^3)$<br\/><span class='basic_pink'>V\u1eady s\u1ed1 ph\u1ea3i \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $240$<\/span><\/span>"}]}],"id_ques":1853},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":5,"ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/9.jpg' \/><\/center>Cho h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng tam gi\u00e1c c\u00f3 \u0111\u00e1y l\u00e0 tam gi\u00e1c vu\u00f4ng c\u00e2n c\u00f3 c\u1ea1nh huy\u1ec1n l\u00e0 $\\sqrt {2}\\,cm$. Chi\u1ec1u cao l\u00e0 $1\\,cm$. T\u00ednh th\u1ec3 t\u00edch h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng.<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/H8_B21_D1.3a.png' \/><\/center><br\/>","select":["A. $1\\,cm^3$","B. $\\sqrt{2}\\,cm^3$","C. $\\dfrac{1}{2}\\,cm^3$","D. $\\dfrac{\\sqrt{2}}{2}\\,cm^3$"],"hint":"\u0110\u1eb7t \u0111\u1ed9 d\u00e0i c\u1ea1nh g\u00f3c vu\u00f4ng c\u1ee7a tam gi\u00e1c \u1edf \u0111\u00e1y l\u00e0 $x$.<br\/>\u00c1p d\u1ee5ng \u0111\u1ecbnh l\u00fd Pytago t\u00ednh \u0111\u1ed9 d\u00e0i m\u1ed7i c\u1ea1nh g\u00f3c vu\u00f4ng.","explain":" <span class='basic_left'><br\/><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/><b>B\u01b0\u1edbc 1:<\/b> G\u1ecdi \u0111\u1ed9 d\u00e0i c\u1ea1nh g\u00f3c vu\u00f4ng c\u1ee7a tam gi\u00e1c \u1edf \u0111\u00e1y l\u00e0 $x$<br\/><b>B\u01b0\u1edbc 2:<\/b> \u00c1p d\u1ee5ng \u0111\u1ecbnh l\u00fd Pytago v\u00e0o tam gi\u00e1c vu\u00f4ng \u1edf \u0111\u00e1y t\u00ecm $x$.<br\/><b>B\u01b0\u1edbc 3:<\/b> T\u00ednh di\u1ec7n t\u00edch \u0111\u00e1y.<br\/><b>B\u01b0\u1edbc 4:<\/b> T\u00ednh th\u1ec3 t\u00edch h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng .<br\/><span class='basic_green'>B\u00e0i gi\u1ea3i<\/span><br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/H8_B21_D1.3b.png' \/><\/center>G\u1ecdi \u0111\u1ed9 d\u00e0i c\u1ea1nh g\u00f3c vu\u00f4ng c\u1ee7a tam gi\u00e1c \u1edf \u0111\u00e1y l\u00e0 $x\\,(cm)$<br\/>Theo \u0111\u1ecbnh l\u00fd Pytago, ta c\u00f3: <br\/>$x^2+x^2=(\\sqrt{2})^2\\\\ \\Leftrightarrow 2x^2=2\\\\ \\Leftrightarrow x=1\\,(cm)$<br\/>V\u1eady di\u1ec7n t\u00edch \u0111\u00e1y l\u00e0 $\\dfrac{1}{2}.1.1=\\dfrac{1}{2}\\,(cm^2)$<br\/>V\u1eady th\u1ec3 t\u00edch c\u1ee7a h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u00e0 $\\dfrac{1}{2}.1=\\dfrac{1}{2}\\,(cm^3)$<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 C <\/span><\/span>","column":2}]}],"id_ques":1854},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[4]],"list":[{"point":5,"ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/H8_B21_D1.7.png' \/><\/center>Cho h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng tam gi\u00e1c \u0111\u1ec1u c\u00f3 di\u1ec7n t\u00edch xung quanh b\u1eb1ng $12 cm^2$. Chi\u1ec1u cao b\u1eb1ng \u0111\u1ed9 d\u00e0i c\u1ea1nh c\u1ee7a tam gi\u00e1c \u1edf \u0111\u00e1y. T\u00ednh th\u1ec3 t\u00edch h\u00ecnh l\u0103ng tr\u1ee5.","select":["A. $4\\sqrt{2}\\,cm^2$","B. $4\\sqrt{3}\\,cm^2$","C. $3\\sqrt{3}\\,cm^2$","D. $2\\sqrt{3}\\,cm^2$"],"hint":"\u0110\u1eb7t \u0111\u1ed9 d\u00e0i c\u1ea1nh tam gi\u00e1c \u0111\u1ec1u l\u00e0 $x$","explain":" <span class='basic_left'><br\/><span class='basic_green'> H\u01b0\u1edbng d\u1eabn:<\/span><br\/><b>B\u01b0\u1edbc 1:<\/b> \u0110\u1eb7t \u1ea9n.<br\/><b>B\u01b0\u1edbc 2:<\/b> Bi\u1ec3u di\u1ec5n di\u1ec7n t\u00edch xung quanh h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng theo $x$.<br\/><b>B\u01b0\u1edbc 3:<\/b> T\u00ecm $x$. T\u00ednh di\u1ec7n t\u00edch \u0111\u00e1y.<br\/><b>B\u01b0\u1edbc 4:<\/b> T\u00ednh th\u1ec3 t\u00edch h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng.<br\/><span class='basic_green'>B\u00e0i gi\u1ea3i<\/span><br\/>G\u1ecdi \u0111\u1ed9 d\u00e0i c\u1ea1nh tam gi\u00e1c \u0111\u1ec1u l\u00e0 $x\\,cm$<br\/>Chu vi tam gi\u00e1c \u1edf \u0111\u00e1y l\u00e0 $3x\\,(cm)$<br\/>Di\u1ec7n t\u00edch xung quanh c\u1ee7a h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u00e0: $3x.x=12\\\\ \\Leftrightarrow 3x^2=12\\\\ \\Leftrightarrow x^2=4\\\\ \\Leftrightarrow x=2\\,(cm^2) \\,\\, (v\u00ec\\,\\, x > 0)$<br\/>Suy ra \u0111\u1ed9 d\u00e0i c\u1ea1nh \u0111\u00e1y l\u00e0 $2\\,cm$<br\/>Ta x\u00e9t \u0111\u00e1y c\u1ee7a l\u0103ng tr\u1ee5 trong h\u00ecnh sau, bi\u1ebft $AM$ l\u00e0 \u0111\u01b0\u1eddng cao.<br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/H8_B21_D1.7b.png' \/><\/center><br\/>X\u00e9t tam gi\u00e1c $ABM$ vu\u00f4ng t\u1ea1i $M$ c\u00f3 $AB=2\\,cm$ v\u00e0 $BM=\\dfrac{1}{2}BC=1\\,cm$<br\/>\u00c1p d\u1ee5ng \u0111\u1ecbnh l\u00fd Pytago, ta c\u00f3:<br\/>$AM=\\sqrt{AB^2-BM^2}=\\sqrt{2^2-1}=\\sqrt{3}\\,(cm)$<br\/>V\u1eady di\u1ec7n t\u00edch \u0111\u00e1y l\u00e0 $\\dfrac{1}{2}.AM.BC=\\dfrac{1}{2}.\\sqrt{3}.2=\\sqrt{3}\\,(cm^2)$<br\/>Th\u1ec3 t\u00edch h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u00e0 $\\sqrt{3}.2=2\\sqrt{3}\\,(cm^3)$<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 D<\/span><\/span>","column":2}]}],"id_ques":1855},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["750"]]],"list":[{"point":5,"width":50,"type_input":"","ques":"Cho h\u00ecnh v\u1ebd, t\u00ednh th\u1ec3 t\u00edch theo k\u00edch th\u01b0\u1edbc cho s\u1eb5n. <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/H8_B21_D1.6.png' \/><\/center><br\/><b> \u0110\u00e1p s\u1ed1: <\/b> _input_($cm^3$)","hint":"T\u00ednh $AB$","explain":"<span class='basic_left'><br\/><span class='basic_green'> H\u01b0\u1edbng d\u1eabn:<\/span><br\/><b>B\u01b0\u1edbc 1:<\/b> T\u00ednh $AB$<br\/><b>B\u01b0\u1edbc 2:<\/b> T\u00ednh di\u1ec7n t\u00edch \u0111\u00e1y<br\/><b>B\u01b0\u1edbc 3:<\/b> T\u00ednh th\u1ec3 t\u00edch h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng .<br\/><span class='basic_green'>B\u00e0i gi\u1ea3i<\/span><br\/>X\u00e9t tam gi\u00e1c $ABC$ vu\u00f4ng t\u1ea1i $B$.<br\/>\u00c1p d\u1ee5ng \u0111\u1ecbnh l\u00fd Pytago, ta c\u00f3:<br\/>$AB^2+BC^2=AC^2\\\\ \\Rightarrow AB^2+12^2=13^2\\\\ \\Leftrightarrow AB^2=169-144\\\\ \\Leftrightarrow AB^2=25\\\\ \\Leftrightarrow AB=5\\,(cm)$<br\/>Di\u1ec7n t\u00edch \u0111\u00e1y h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u00e0 $\\dfrac{1}{2}.5.12=30\\,(cm^2)$<br\/>Th\u1ec3 t\u00edch h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u00e0 $30.25=750\\,(cm^3)$<br\/><span class='basic_pink'>V\u1eady s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $750$<\/span><br\/><b>Ch\u00fa \u00fd:<\/b> H\u00ecnh v\u1ebd l\u00e0 l\u0103ng tr\u1ee5 \u0111\u1ee9ng c\u00f3 \u0111\u00e1y l\u00e0 hai tam gi\u00e1c vu\u00f4ng $ABC$ v\u00e0 $DEF$ v\u00e0 chi\u1ec1u cao l\u00e0 $CF$. Tr\u00e1nh nh\u1ea7m l\u1eabn \u0111\u00e1y l\u00e0 t\u1ee9 gi\u00e1c $BEFC$<\/span>"}]}],"id_ques":1856},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["117"]]],"list":[{"point":5,"width":50,"type_input":"","ques":"Cho h\u00ecnh v\u1ebd, t\u00ednh th\u1ec3 t\u00edch theo k\u00edch th\u01b0\u1edbc cho s\u1eb5n. <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/H8_B21_D1.9.png' \/><\/center><br\/><b> \u0110\u00e1p s\u1ed1: <\/b> _input_($cm^3$)","hint":"T\u00ednh \u0111\u1ed9 d\u00e0i c\u1ea1nh huy\u1ec1n r\u1ed3i t\u00ednh di\u1ec7n t\u00edch \u0111\u00e1y","explain":"<span class='basic_left'><br\/><span class='basic_green'> H\u01b0\u1edbng d\u1eabn:<\/span><br\/><b>B\u01b0\u1edbc 1:<\/b> T\u00ednh $BC$<br\/><b>B\u01b0\u1edbc 2:<\/b> T\u00ednh di\u1ec7n t\u00edch tam gi\u00e1c $ABC$ v\u00e0 h\u00ecnh ch\u1eef nh\u1eadt $BCMN$<br\/><b>B\u01b0\u1edbc 3:<\/b> T\u00ednh di\u1ec7n t\u00edch \u0111\u00e1y.<br\/><b>B\u01b0\u1edbc 4:<\/b> T\u00ednh th\u1ec3 t\u00edch h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng.<br\/><span class='basic_green'>B\u00e0i gi\u1ea3i<\/span><br\/>\u0110\u00e1y h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng \u0111\u01b0\u1ee3c gh\u00e9p b\u1edfi tam gi\u00e1c vu\u00f4ng $ABC$ v\u00e0 h\u00ecnh ch\u1eef nh\u1eadt $BCMN$<br\/>X\u00e9t tam gi\u00e1c vu\u00f4ng $ABC$. \u00c1p d\u1ee5ng \u0111\u1ecbnh l\u00fd Pytago ta c\u00f3:<br\/>$BC^2=AB^2+AC^2\\\\ \\Rightarrow BC^2=3^2+4^2\\\\ \\Leftrightarrow BC=5\\,(cm)$<br\/>Di\u1ec7n t\u00edch tam gi\u00e1c $ABC$ l\u00e0 $\\dfrac{1}{2}.3.4=6\\,(cm^2)$<br\/>Di\u1ec7n t\u00edch h\u00ecnh ch\u1eef nh\u1eadt $BCMN$ l\u00e0 $5.2,4=12\\,(cm^2)$<br\/>Di\u1ec7n t\u00edch \u0111\u00e1y c\u1ee7a h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u00e0 $S_{ABC}+S_{BCMN}=6+12=18\\,(cm^2)$<br\/>Th\u1ec3 t\u00edch h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u00e0 $18.6,5=117\\,(cm^3)$<br\/><span class='basic_pink'>V\u1eady s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $117$<\/span><\/span>"}]}],"id_ques":1857},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["5"]]],"list":[{"point":5,"width":50,"type_input":"","ques":"Cho h\u00ecnh v\u1ebd. Bi\u1ebft th\u1ec3 t\u00edch c\u1ee7a h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng t\u1ee9 gi\u00e1c l\u00e0 $15\\,cm^3$. T\u00ednh chi\u1ec1u cao h\u00ecnh l\u0103ng tr\u1ee5. <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/H8_B21_D1.8.png' \/><\/center><br\/><b> \u0110\u00e1p s\u1ed1: <\/b> _input_($cm^3$)","hint":"\u0110\u00e1y l\u00e0 h\u00ecnh thang.","explain":"<span class='basic_left'>H\u00ecnh v\u1ebd tr\u00ean l\u00e0 h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng c\u00f3 $2$ \u0111\u00e1y $HKJI$ v\u00e0 $ DGLM$ l\u00e0 c\u00e1c h\u00ecnh thang.<br\/>\u0110\u00e1y $HKJI$ c\u00f3 di\u1ec7n t\u00edch l\u00e0 $\\dfrac{1}{2}.1,2.(1,2+3,8)=3\\,(cm^3)$<br\/>V\u1eady chi\u1ec1u cao h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u00e0 $15:3=5\\,(cm)$ <br\/><span class='basic_pink'>V\u1eady s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $5$<\/span><\/span>"}]}],"id_ques":1858},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[4]],"list":[{"point":5,"ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/2.jpg' \/><\/center>M\u1ed9t h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt c\u00f3 k\u00edch th\u01b0\u1edbc m\u1ed9t c\u1ea1nh c\u1ee7a m\u1eb7t \u0111\u00e1y l\u00e0 $15\\,cm$. T\u00ednh k\u00edch th\u01b0\u1edbc c\u00f2n l\u1ea1i c\u1ee7a \u0111\u00e1y bi\u1ebft r\u1eb1ng s\u1ed1 \u0111o di\u1ec7n t\u00edch xung quanh c\u1ee7a h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt b\u1eb1ng s\u1ed1 \u0111o th\u1ec3 t\u00edch.","select":["A. $\\dfrac{17}{30}\\,cm$","B. $\\dfrac{13}{30}\\,cm$","C. $\\dfrac{30}{17}\\,cm$","D. $\\dfrac{30}{13}\\,cm$"],"hint":"G\u1ecdi k\u00edch th\u01b0\u1edbc \u0111\u00e1y c\u00f2n l\u1ea1i v\u00e0 chi\u1ec1u cao h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u00e0 $a$ v\u00e0 $b$.","explain":" <span class='basic_left'><br\/><span class='basic_green'> H\u01b0\u1edbng d\u1eabn:<\/span><br\/><b>B\u01b0\u1edbc 1:<\/b> G\u1ecdi k\u00edch th\u01b0\u1edbc \u0111\u00e1y c\u00f2n l\u1ea1i v\u00e0 chi\u1ec1u cao h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng l\u00e0 $a$ v\u00e0 $b$.<br\/><b>B\u01b0\u1edbc 2:<\/b> Bi\u1ec3u di\u1ec5n bi\u1ec3u th\u1ee9c t\u00ednh di\u1ec7n t\u00edch xung quanh theo $a$ v\u00e0 $b$<br\/><b>B\u01b0\u1edbc 3:<\/b> Bi\u1ec3u di\u1ec7n bi\u1ec3u th\u1ee9c t\u00ednh th\u1ec3 t\u00edch h\u00ecnh l\u0103ng tr\u1ee5 \u0111\u1ee9ng theo $a$ v\u00e0 $b$<br\/><b>B\u01b0\u1edbc 4:<\/b> Gi\u1ea3i t\u00ecm $a$<br\/><span class='basic_green'>B\u00e0i gi\u1ea3i<\/span><br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai21/lv1/img\/H8_B21_D1.22.png' \/><\/center>G\u1ecdi k\u00edch th\u01b0\u1edbc \u0111\u00e1y v\u00e0 chi\u1ec1u cao c\u1ee7a h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt l\u00e0 $a$ v\u00e0 $b$ ($cm$)<br\/>Di\u1ec7n t\u00edch xung quanh c\u1ee7a h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt l\u00e0 $(15+a).2.b$ ($cm^2$)<br\/>Th\u1ec3 t\u00edch c\u1ee7a h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt l\u00e0 $15.a.b\\,(cm^3)$<br\/>V\u00ec s\u1ed1 \u0111o di\u1ec7n t\u00edch xung quanh c\u1ee7a h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt b\u1eb1ng s\u1ed1 \u0111o th\u1ec3 t\u00edch n\u00ean ta c\u00f3:<br\/>$(15+a).2.b=15ab\\Leftrightarrow (15+a).2=15a\\Leftrightarrow 13a=30\\Leftrightarrow a=\\dfrac{30}{13}\\,(cm)$<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 D<\/span><\/span>","column":2}]}],"id_ques":1859}],"lesson":{"save":0,"level":1}}