{"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":" <span class='basic_left'> H\u00ecnh vu\u00f4ng l\u00e0 t\u1ee9 gi\u00e1c: <\/span>","select":[" A. C\u00f3 hai \u0111\u01b0\u1eddng ch\u00e9o b\u1eb1ng nhau v\u00e0 vu\u00f4ng g\u00f3c v\u1edbi nhau"," B. C\u00f3 hai \u0111\u01b0\u1eddng ch\u00e9o b\u1eb1ng nhau v\u00e0 c\u1eaft nhau t\u1ea1i trung \u0111i\u1ec3m c\u1ee7a m\u1ed7i \u0111\u01b0\u1eddng"," C. C\u00f3 hai \u0111\u01b0\u1eddng ch\u00e9o vu\u00f4ng g\u00f3c v\u00e0 c\u1eaft nhau t\u1ea1i trung \u0111i\u1ec3m c\u1ee7a m\u1ed7i \u0111\u01b0\u1eddng "," D. C\u1ea3 ba \u0111\u00e1p \u00e1n A, B, C tr\u00ean \u0111\u1ec1u sai"],"explain":" <span class='basic_left'> C\u1ea3 ba \u0111\u00e1p \u00e1n A, B, C \u0111\u1ec1u sai v\u00ec: H\u00ecnh vu\u00f4ng l\u00e0 t\u1ee9 gi\u00e1c c\u00f3 hai \u0111\u01b0\u1eddng ch\u00e9o b\u1eb1ng nhau v\u00e0 vu\u00f4ng g\u00f3c v\u1edbi nhau t\u1ea1i trung \u0111i\u1ec3m m\u1ed7i \u0111\u01b0\u1eddng. <br\/> Do \u0111\u00f3 c\u00e2u D l\u00e0 \u0111\u00fang. <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 D. <\/span><\/span> ","column":1}]}],"id_ques":1491},{"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":" <span class='basic_left'> <b> H\u00ecnh thoi c\u00f3 ________ l\u00e0 h\u00ecnh vu\u00f4ng. <\/b> <br\/> C\u1ea7n \u0111i\u1ec1n v\u00e0o ch\u1ed7 tr\u1ed1ng l\u00e0: <\/span>","select":[" A. Hai \u0111\u01b0\u1eddng ch\u00e9o b\u1eb1ng nhau"," B. M\u1ed9t \u0111\u01b0\u1eddng ch\u00e9o l\u00e0 ph\u00e2n gi\u00e1c c\u1ee7a m\u1ed9t g\u00f3c"," C. Hai \u0111\u01b0\u1eddng ch\u00e9o c\u1eaft nhau t\u1ea1i trung \u0111i\u1ec3m c\u1ee7a m\u1ed7i \u0111\u01b0\u1eddng"," D. Hai c\u1ea1nh \u0111\u1ed1i song song"],"explain":" <span class='basic_left'> H\u00ecnh thoi c\u00f3 hai \u0111\u01b0\u1eddng ch\u00e9o b\u1eb1ng nhau l\u00e0 h\u00ecnh vu\u00f4ng. <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 A. <\/span><\/span> ","column":1}]}],"id_ques":1492},{"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":" <span class='basic_left'> H\u00ecnh vu\u00f4ng c\u00f3 m\u1ea5y tr\u1ee5c \u0111\u1ed1i x\u1ee9ng? <\/span>","select":[" A. 4"," B. 3"," C. 2"," D. 1"],"explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai8/lv1/img\/H815_D2_4.jpg' \/><\/center> H\u00ecnh vu\u00f4ng c\u00f3 4 tr\u1ee5c \u0111\u1ed1i x\u1ee9ng nh\u01b0 h\u00ecnh v\u1ebd tr\u00ean. <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 A. <\/span><\/span> ","column":4}]}],"id_ques":1493},{"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":" <span class='basic_left'> Cho h\u00ecnh vu\u00f4ng $MNPQ$ c\u1ea1nh c\u00f3 \u0111\u1ed9 d\u00e0i l\u00e0 $8 cm$. T\u00ednh \u0111\u1ed9 d\u00e0i \u0111\u01b0\u1eddng ch\u00e9o $NQ$. <\/span>","select":[" A. $NQ = 4\\, cm$"," B. $NQ = 4\\sqrt{2}\\, cm$"," C. $NQ = 8\\sqrt{2}\\, cm$"," D. $NQ = 2\\sqrt{2}\\, cm$"],"explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai8/lv1/img\/H818_D1_1.jpg' \/><\/center> X\u00e9t tam gi\u00e1c vu\u00f4ng $NPQ$ c\u00f3: <br\/> $NQ^2=NP^2+PQ^2$ (\u0111\u1ecbnh l\u00fd Pi- ta - go) <br\/> $\\Rightarrow NQ^2=8^2+8^2=2.8^2$ <br\/> $\\Rightarrow NQ=8\\sqrt{2}\\, (cm)$ <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 C. <\/span><\/span> ","column":4}]}],"id_ques":1494},{"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":" <span class='basic_left'> Cho h\u00ecnh vu\u00f4ng $ABCD$, \u0111i\u1ec3m $O$ l\u00e0 giao c\u1ee7a hai \u0111\u01b0\u1eddng ch\u00e9o. Bi\u1ebft $OC = 10 cm$, \u0111\u1ed9 d\u00e0i \u0111\u01b0\u1eddng ch\u00e9o $BD$ l\u00e0: <\/span>","select":[" A. $ 10\\, cm$"," B. $ 15\\, cm$"," C. $20\\, cm$"," D. $25\\, cm$"],"explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai8/lv1/img\/H818_D1_2.jpg' \/><\/center> Do $OC =10\\, cm$ v\u00e0 $AC=2OC$ n\u00ean $AC=20\\, (cm)$ <br\/> Do $ABCD$ l\u00e0 h\u00ecnh vu\u00f4ng n\u00ean: $AC=BD$ <br\/>$\\Rightarrow BD=20\\, cm$. <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 C. <\/span><\/span> ","column":4}]}],"id_ques":1495},{"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":" <span class='basic_left'> Cho h\u00ecnh vu\u00f4ng $ABCD$, \u0111i\u1ec3m $O$ l\u00e0 giao c\u1ee7a hai \u0111\u01b0\u1eddng ch\u00e9o. Bi\u1ebft $AB = 10 cm$, \u0111\u1ed9 d\u00e0i \u0111\u01b0\u1eddng ch\u00e9o $AC$ l\u00e0: <\/span>","select":[" A. $ 15\\, cm$"," B. $ 20\\, cm$"," C. $10\\sqrt{2}\\, cm$"," D. $2\\sqrt{6}\\, cm$"],"explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai8/lv1/img\/H818_D2_4.jpg' \/><\/center> Trong h\u00ecnh vu\u00f4ng $ABCD$ c\u00f3: $AC\\bot BD$ n\u00ean $\\Delta OAB$ vu\u00f4ng t\u1ea1i $O$ <br\/> X\u00e9t $\\Delta OAB$: <br\/> $AB^2=OA^2+OB^2=2OA^2$ (do $OA=OB=\\dfrac{1}{2}AC$) <br\/> $\\Rightarrow OA^2=AB^2:2$ <br\/> $\\Rightarrow OA^2=10^2:2=50$ <br\/> $\\Rightarrow OA=5\\sqrt{2}\\, (cm)$ <br\/> M\u00e0 $AC=2OA$ n\u00ean $AC=2.5\\sqrt{2}=10\\sqrt{2}\\, (cm)$ <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 C. <\/span><\/span> ","column":2}]}],"id_ques":1496},{"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":" <span class='basic_left'> Cho h\u00ecnh vu\u00f4ng $MNPQ$, \u0111i\u1ec3m $O$ l\u00e0 giao c\u1ee7a hai \u0111\u01b0\u1eddng ch\u00e9o. Tam gi\u00e1c $NOP$ l\u00e0 tam gi\u00e1c g\u00ec? <\/span>","select":[" A. Tam gi\u00e1c vu\u00f4ng","B. Tam gi\u00e1c c\u00e2n"," C. Tam gi\u00e1c vu\u00f4ng c\u00e2n"],"explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai8/lv1/img\/H818_D1_4.jpg' \/><\/center> Trong h\u00ecnh vu\u00f4ng $MNPQ$ th\u00ec: $MP\\bot NQ$ n\u00ean $\\Delta NOP$ vu\u00f4ng t\u1ea1i $O$. <br\/> M\u00e0 $NO=PO$ (t\u00ednh ch\u1ea5t). <br\/> Do \u0111\u00f3: $\\Delta NOP$ vu\u00f4ng c\u00e2n t\u1ea1i $O$. <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 C. <\/span><\/span> ","column":3}]}],"id_ques":1497},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang ho\u1eb7c sai","title_trans":"\u0110\u1ec1 chung cho ba c\u00e2u","temp":"multiple_choice","correct":[[1]],"list":[{"point":5,"ques":" <span class='basic_left'> Cho h\u00ecnh vu\u00f4ng $ABCD$. Tr\u00ean tia \u0111\u1ed1i c\u1ee7a tia $AD, BA, CB, DC$ l\u1ea5y c\u00e1c \u0111i\u1ec3m $A', B', C', D'$ sao cho $AA'=BB'=CC'=DD'$ <br\/> <b> C\u00e2u 1:<\/b> Ta ch\u1ee9ng minh \u0111\u01b0\u1ee3c $\\Delta AA'B' = \\Delta BB'C'=\\Delta CC'D'=\\Delta DD'A'$. <\/span>","select":[" \u0110\u00fang"," Sai"],"explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai8/lv1/img\/H818_D1_5.jpg' \/><\/center> X\u00e9t c\u00e1c tam gi\u00e1c $\\Delta AA'B' ; \\Delta BB'C';\\Delta CC'D';\\Delta DD'A'$ <br\/> + $AA'=BB'=CC'=DD'$ (gi\u1ea3 thi\u1ebft) <br\/> + $\\widehat{A'AB'}=\\widehat{B'BC'}=\\widehat{C'CD'}=\\widehat{D'DA'}=90^o$ <br\/> + $AB'=BC'=CD'=DA'$ <br\/> $\\Rightarrow \\Delta AA'B' = \\Delta BB'C'=\\Delta CC'D'=\\Delta DD'A'$ (c - g - c). <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 \u0110\u00fang. <\/span><\/span> ","column":2}]}],"id_ques":1498},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"\u0110\u1ec1 chung cho ba c\u00e2u","temp":"fill_the_blank","correct":[[["90"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<span class='basic_left'> Cho h\u00ecnh vu\u00f4ng $ABCD$. Tr\u00ean tia \u0111\u1ed1i c\u1ee7a tia $AD, BA, CB, DC$ l\u1ea5y c\u00e1c \u0111i\u1ec3m $A', B', C', D'$ sao cho $AA'=BB'=CC'=DD'$. <br\/> <b> C\u00e2u 2:<\/b> T\u00ednh $\\widehat{A'B'C'}$. <br\/><br\/> <b> \u0110\u00e1p \u00e1n:<\/b> $\\widehat{A'B'C'}=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}^o$ <\/span> ","explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai8/lv1/img\/H818_D1_5.jpg' \/><\/center> X\u00e9t $\\Delta AA'B'$ c\u00f3: $\\widehat{AA'B'}+\\widehat{A'B'A}=90^o$ <br\/> M\u00e0 $\\widehat{AA'B'}=\\widehat{BB'C'}$ (do $\\Delta AA'B'=\\Delta BB'C'$) <br\/> $\\Rightarrow \\widehat{A'B'A}+\\widehat{BB'C'}=90^o$ <br\/> $\\Rightarrow \\widehat{A'B'C'}=90^o$ <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o c\u00e1c \u00f4 tr\u1ed1ng l\u00e0 $90$. <\/span> <\/span> "}]}],"id_ques":1499},{"time":24,"part":[{"title":"Kh\u1eb3ng \u0111\u1ecbnh sau \u0111\u00e2y \u0111\u00fang hay sai.","title_trans":"\u0110\u1ec1 chung cho ba c\u00e2u","temp":"multiple_choice","correct":[[1]],"list":[{"point":5,"ques":" <span class='basic_left'> Cho h\u00ecnh vu\u00f4ng $ABCD$. Tr\u00ean tia \u0111\u1ed1i c\u1ee7a tia $AD, BA, CB, DC$ l\u1ea5y c\u00e1c \u0111i\u1ec3m $A', B', C', D'$ sao cho $AA'=BB'=CC'=DD'$. <br\/> <b> C\u00e2u 3:<\/b> T\u1ee9 gi\u00e1c $A'B'C'D'$ l\u00e0 h\u00ecnh vu\u00f4ng. <\/span>","select":[" \u0110\u00fang"," Sai"],"explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai8/lv1/img\/H818_D1_5.jpg' \/><\/center> Theo c\u00e2u 1, ta \u0111\u00e3 ch\u1ee9ng minh \u0111\u01b0\u1ee3c: $\\Delta AA'B' = \\Delta BB'C'=\\Delta CC'D'=\\Delta DD'A'$ <br\/> $\\Rightarrow A'B'=B'C'=C'D'=D'A'$ (c\u00e1c c\u1ea1nh t\u01b0\u01a1ng \u1ee9ng) <br\/> Do \u0111\u00f3 t\u1ee9 gi\u00e1c $A'B'C'D'$ l\u00e0 h\u00ecnh thoi (d\u1ea5u hi\u1ec7u nh\u1eadn bi\u1ebft) <br\/> M\u1eb7t kh\u00e1c, c\u00e2u 2 ta ch\u1ee9ng minh \u0111\u01b0\u1ee3c $\\widehat{A'B'C'}=90^o$ <br\/> $\\Rightarrow A'B'C'D'$ l\u00e0 h\u00ecnh vu\u00f4ng (d\u1ea5u hi\u1ec7u nh\u1eadn bi\u1ebft). <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 \u0110\u00fang. <\/span><\/span> ","column":2}]}],"id_ques":1500},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang ho\u1eb7c sai","title_trans":"\u0110\u1ec1 chung cho ba c\u00e2u","temp":"multiple_choice","correct":[[1]],"list":[{"point":5,"ques":" <span class='basic_left'> Cho $\\Delta ABC$ c\u00e2n $A$ c\u00f3 $AB=\\sqrt{2}\\, cm; BC=2\\, cm$. \u0110i\u1ec3m $D$ \u0111\u1ed1i x\u1ee9ng v\u1edbi $A$ qua $BC$. <br\/> <b> C\u00e2u 1:<\/b> Ta ch\u1ee9ng minh \u0111\u01b0\u1ee3c $\\Delta ABC$ l\u00e0 tam gi\u00e1c vu\u00f4ng c\u00e2n. <\/span>","select":[" \u0110\u00fang"," Sai"],"explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai8/lv1/img\/H818_D1_6a.jpg' \/><\/center> Do $\\Delta ABC$ c\u00e2n t\u1ea1i $A$ n\u00ean $AB=AC=\\sqrt{2}\\, (cm)$ <br\/> Do \u0111\u00f3, ta th\u1ea5y: $(\\sqrt{2})^2+(\\sqrt{2})^2=2^2$, t\u1ee9c l\u00e0: $AB^2+AC^2=BC^2$ <br\/> $\\Rightarrow \\Delta ABC$ vu\u00f4ng c\u00e2n t\u1ea1i $A$. <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 \u0110\u00fang. <\/span><\/span> ","column":2}]}],"id_ques":1501},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"\u0110\u1ec1 chung cho ba c\u00e2u","temp":"fill_the_blank","correct":[[["90"]]],"list":[{"point":5,"width":40,"type_input":"","ques":" <span class='basic_left'> Cho $\\Delta ABC$ c\u00e2n $A$ c\u00f3 $AB=\\sqrt{2}\\, cm; BC=2\\, cm$. \u0110i\u1ec3m $D$ \u0111\u1ed1i x\u1ee9ng v\u1edbi $A$ qua $BC$. <br\/> <b> C\u00e2u 2:<\/b> T\u00ednh $\\widehat{ABD}$. <br\/><br\/> <b> \u0110\u00e1p \u00e1n:<\/b> $\\widehat{ABD}= \\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}^o$ <\/span> ","explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai8/lv1/img\/H818_D1_6.jpg' \/><\/center> Theo b\u00e0i, $D$ l\u00e0 \u0111i\u1ec3m \u0111\u1ed1i x\u1ee9ng v\u1edbi $A$ qua $BC$ <br\/> G\u1ecdi $AD\\cap BC=H$ <br\/> $\\Rightarrow AH=HD; AD\\bot BC$ t\u1ea1i $H$. <br\/> Do \u0111\u00f3 $\\Delta ABD$ c\u00e2n t\u1ea1i $B$ (1) <br\/> M\u1eb7t kh\u00e1c: $AH$ l\u00e0 ph\u00e2n gi\u00e1c c\u1ee7a $\\widehat{BAC}$ n\u00ean $\\widehat{BAH}=45^o$ (2) <br\/> T\u1eeb (1) v\u00e0 (2) suy ra $\\widehat{ABD}=90^o$. <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o c\u00e1c \u00f4 tr\u1ed1ng l\u00e0 $90$. <\/span> <\/span> "}]}],"id_ques":1502},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"\u0110\u1ec1 chung cho ba c\u00e2u","temp":"multiple_choice","correct":[[3]],"list":[{"point":5,"ques":" <span class='basic_left'> Cho $\\Delta ABC$ c\u00e2n t\u1ea1i $A$ c\u00f3 $AB=\\sqrt{2}\\, cm; BC=2\\, cm$. \u0110i\u1ec3m $D$ \u0111\u1ed1i x\u1ee9ng v\u1edbi $A$ qua $BC$. <br\/> <b> C\u00e2u 3:<\/b> T\u1ee9 gi\u00e1c $ABDC$ l\u00e0 h\u00ecnh g\u00ec? <\/span>","select":[" A. H\u00ecnh b\u00ecnh h\u00e0nh"," B. H\u00ecnh ch\u1eef nh\u1eadt","C. H\u00ecnh vu\u00f4ng","D. H\u00ecnh thoi"],"explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai8/lv1/img\/H818_D1_6.jpg' \/><\/center> Theo c\u00e2u 1, ta \u0111\u00e3 ch\u1ec9 ra \u0111\u01b0\u1ee3c $AH=HD$ (1) <br\/> H\u01a1n n\u1eefa $\\Delta ABC$ vu\u00f4ng c\u00e2n t\u1ea1i $A$ (theo c\u00e2u 1) m\u00e0 $AH\\bot BC$ n\u00ean $BH=HC$ (2) <br\/> T\u1eeb (1) v\u00e0 (2) suy ra $ABDC$ l\u00e0 h\u00ecnh b\u00ecnh h\u00e0nh (d\u1ea5u hi\u1ec7u nh\u1eadn bi\u1ebft) <br\/> M\u1eb7t kh\u00e1c: $AD \\bot BC$ t\u1ea1i $H$ n\u00ean $ABDC$ l\u00e0 h\u00ecnh thoi (d\u1ea5u hi\u1ec7u nh\u1eadn bi\u1ebft). <br\/> L\u1ea1i c\u00f3: $\\widehat{BAC}=90^o$ n\u00ean $ABDC$ l\u00e0 h\u00ecnh vu\u00f4ng (d\u1ea5u hi\u1ec7u nh\u1eadn bi\u1ebft). <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 C. <\/span><\/span> ","column":2}]}],"id_ques":1503},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"\u0110\u1ec1 chung cho hai c\u00e2u","temp":"multiple_choice","correct":[[3]],"list":[{"point":5,"ques":" <span class='basic_left'> Cho h\u00ecnh ch\u1eef nh\u1eadt $ABCD$ c\u00f3 $AB=2BC$. G\u1ecdi $I$ l\u00e0 trung \u0111i\u1ec3m c\u1ee7a $AB$ v\u00e0 $K$ l\u00e0 trung \u0111i\u1ec3m c\u1ee7a $DC$ <br\/> <b> C\u00e2u 1:<\/b> T\u1ee9 gi\u00e1c $AIKD$ v\u00e0 $BIKC$ l\u00e0 h\u00ecnh g\u00ec? <\/span>","select":[" A. H\u00ecnh b\u00ecnh h\u00e0nh"," B. H\u00ecnh ch\u1eef nh\u1eadt","C. H\u00ecnh vu\u00f4ng","D. H\u00ecnh thoi"],"explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai8/lv1/img\/H818_D1_7.jpg' \/><\/center> X\u00e9t t\u1ee9 gi\u00e1c $AIKD$ c\u00f3: $AI=IK=DK=AD$ (gi\u1ea3 thi\u1ebft) v\u00e0 $\\widehat{A}=90^o$ <br\/> Do \u0111\u00f3 $AIKD$ l\u00e0 h\u00ecnh vu\u00f4ng (d\u1ea5u hi\u1ec7u nh\u1eadn bi\u1ebft). <br\/> T\u01b0\u01a1ng t\u1ef1 ta c\u00f3: T\u1ee9 gi\u00e1c $BIKC$ l\u00e0 h\u00ecnh vu\u00f4ng. <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 C. <\/span><\/span> ","column":2}]}],"id_ques":1504},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"\u0110\u1ec1 chung cho hai c\u00e2u","temp":"multiple_choice","correct":[[1]],"list":[{"point":5,"ques":" <span class='basic_left'> Cho h\u00ecnh ch\u1eef nh\u1eadt $ABCD$ c\u00f3 $AB=2BC$. G\u1ecdi $I$ l\u00e0 trung \u0111i\u1ec3m c\u1ee7a $AB$ v\u00e0 $K$ l\u00e0 trung \u0111i\u1ec3m c\u1ee7a $DC$ <br\/> <b> C\u00e2u 2:<\/b> S\u1ed1 \u0111o c\u1ee7a $\\widehat{DIC}$ l\u00e0: <\/span>","select":[" A. $90^o$"," B. $45^o$","C. $80^o$","D. $100^o$"],"hint":"$\\widehat{DIC}=\\widehat{DIK}+\\widehat{CIK}$","explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai8/lv1/img\/H818_D1_7.jpg' \/><\/center> Theo c\u00e2u 1, ta ch\u1ee9ng minh \u0111\u01b0\u1ee3c $AIKD$ l\u00e0 h\u00ecnh vu\u00f4ng <br\/> M\u00e0 $DI$ l\u00e0 \u0111\u01b0\u1eddng ch\u00e9o n\u00ean c\u0169ng l\u00e0 ph\u00e2n gi\u00e1c c\u1ee7a g\u00f3c $AIK$. <br\/> $\\Rightarrow \\widehat{DIK}=45^o$ (1)<br\/> T\u1ee9 gi\u00e1c $BIKC$ l\u00e0 h\u00ecnh vu\u00f4ng (theo c\u00e2u 1) <br\/> M\u00e0 $CI$ l\u00e0 \u0111\u01b0\u1eddng ch\u00e9o \u0111\u1ed3ng th\u1eddi l\u00e0 ph\u00e2n gi\u00e1c c\u1ee7a g\u00f3c $BIK$. <br\/> $\\Rightarrow \\widehat{CIK}=45^o$ (2)<br\/> T\u1eeb (1) v\u00e0 (2) suy ra: $\\widehat{DIC}=\\widehat{DIK}+\\widehat{CIK}=90^o$. <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 A. <\/span><\/span> ","column":4}]}],"id_ques":1505},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"\u0110\u1ec1 chung cho hai c\u00e2u","temp":"multiple_choice","correct":[[3]],"list":[{"point":5,"ques":" <span class='basic_left'> Cho h\u00ecnh vu\u00f4ng $ABCD$ c\u00f3 c\u1ea1nh b\u1eb1ng $17 cm$. Tr\u00ean c\u00e1c c\u1ea1nh $AB, BC, CD, DA$ l\u1ea5y theo th\u1ee9 t\u1ef1 c\u00e1c \u0111i\u1ec3m $E, F, G, H$ sao cho $AE = BF = CG = DH = 5\\, cm$. <br\/> <b> C\u00e2u 1:<\/b> T\u1ee9 gi\u00e1c $EFGH$ l\u00e0 h\u00ecnh g\u00ec? <\/span>","select":[" A. H\u00ecnh b\u00ecnh h\u00e0nh"," B. H\u00ecnh ch\u1eef nh\u1eadt","C. H\u00ecnh vu\u00f4ng","D. H\u00ecnh thoi"],"explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai8/lv1/img\/H818_D1_8.jpg' \/><\/center> X\u00e9t $\\Delta$ $AEH$ v\u00e0 $\\Delta$ $BFE$ c\u00f3: <br\/> + $AE = BF$ <br\/> + $\\widehat{EAH}=\\widehat{FBE}={{90}^{o}}$<br\/> + $AH = BE$<br\/> $\\begin{align} & \\Rightarrow \\Delta \\,AEH=\\Delta \\,BFE\\,\\,\\,\\left( c-g-c \\right) \\\\ & \\Rightarrow EH=FE;\\,\\,\\,{{\\widehat{H}}_{1}}={{\\widehat{E}}_{1}} \\\\ \\end{align}$ <br\/> M\u00e0 ${{\\widehat{H}}_{1}}+{{\\widehat{E}}_{2}}={{90}^{o}}\\Rightarrow {{\\widehat{E}}_{1}}+{{\\widehat{E}}_{2}}={{90}^{o}}\\Rightarrow \\widehat{HE\\,F}={{90}^{o}}$ (1) <br\/> Ch\u1ee9ng minh t\u01b0\u01a1ng t\u1ef1 ta c\u00f3: $\\Delta$ $BFE =$ $\\Delta$ $CGF =$ $\\Delta$ $DHG$ (c \u2013 g \u2013 c) <br\/> $\\Rightarrow \\widehat{E\\,FG}=\\widehat{FGH}={{90}^{o}}$ (2) <br\/> T\u1eeb (1) v\u00e0 (2) suy ra $EFGH$ l\u00e0 h\u00ecnh ch\u1eef nh\u1eadt, l\u1ea1i c\u00f3 $EH = FE$ n\u00ean $EFGH$ l\u00e0 h\u00ecnh vu\u00f4ng. <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 C. <\/span><\/span> ","column":2}]}],"id_ques":1506},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"\u0110\u1ec1 chung cho hai c\u00e2u","temp":"multiple_choice","correct":[[4]],"list":[{"point":5,"ques":" <span class='basic_left'> Cho h\u00ecnh vu\u00f4ng $ABCD$ c\u00f3 c\u1ea1nh b\u1eb1ng $17 cm$. Tr\u00ean c\u00e1c c\u1ea1nh $AB, BC, CD, DA$ l\u1ea5y theo th\u1ee9 t\u1ef1 c\u00e1c \u0111i\u1ec3m $E, F, G, H$ sao cho $AE = BF = CG = DH = 5\\, cm$. <br\/> <b> C\u00e2u 2:<\/b> \u0110\u1ed9 d\u00e0i $EH$ l\u00e0: <\/span>","select":[" A. $10 cm$"," B. $11 cm$","C. $12 cm$","D. $13 cm$"],"explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai8/lv1/img\/H818_D1_8.jpg' \/><\/center> Do $ABCD$ l\u00e0 h\u00ecnh vu\u00f4ng c\u1ea1nh $17\\,cm$, t\u1ee9c l\u00e0 $AD=17\\,cm$ <br\/> Ta c\u00f3: $AD=AH+HD$ <br\/> $\\Rightarrow AH=AD-HD=17-5=12\\,(cm)$ <br\/> X\u00e9t $\\Delta$ $AEH$ vu\u00f4ng t\u1ea1i $A$ , \u00e1p d\u1ee5ng \u0111\u1ecbnh l\u00fd Pi \u2013 ta \u2013 go c\u00f3: <br\/> $\\begin{align} & E{{H}^{2}}=A{{E}^{2}}+A{{H}^{2}}={{5}^{2}}+{{12}^{2}} \\\\ & EH=13\\,\\,(cm) \\\\ \\end{align}$ <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 D. <\/span><\/span> ","column":4}]}],"id_ques":1507},{"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":" <span class='basic_left'> H\u00ecnh vu\u00f4ng c\u00f3 chu vi l\u00e0 $48 cm$. \u0110\u1ed9 \u0111\u00e0i \u0111\u01b0\u1eddng ch\u00e9o c\u1ee7a h\u00ecnh vu\u00f4ng \u0111\u00f3 l\u00e0: <\/span>","select":[" A. $24\\, cm$"," B. $12\\, cm$","C. $12\\sqrt{2}\\, cm$","D. $6\\sqrt{2}\\, cm$"],"explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai8/lv1/img\/H818_D1_9.jpg' \/><\/center> \u0110\u1ed9 d\u00e0i c\u1ea1nh c\u1ee7a h\u00ecnh vu\u00f4ng \u0111\u00f3 l\u00e0: <br\/> $48:4=12\\, (cm)$ <br\/> \u0110\u1ed9 d\u00e0i \u0111\u01b0\u1eddng ch\u00e9o c\u1ee7a h\u00ecnh vu\u00f4ng \u0111\u00f3 l\u00e0: <br\/> $\\sqrt{12^2+12^2}=12\\sqrt{2}\\, (cm)$ <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 C. <\/span><\/span> ","column":4}]}],"id_ques":1508},{"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":" <span class='basic_left'> H\u00ecnh vu\u00f4ng c\u00f3 \u0111\u1ed9 d\u00e0i \u0111\u01b0\u1eddng ch\u00e9o l\u00e0 $20 cm$ th\u00ec chu vi c\u1ee7a h\u00ecnh vu\u00f4ng \u0111\u00f3 l\u00e0: <\/span>","select":[" A. $20\\sqrt{2}\\, cm$"," B. $40\\sqrt{2}\\, cm$","C. $100\\, cm$","D. $40\\, cm$"],"Hint":" T\u00ednh \u0111\u1ed9 d\u00e0i c\u1ea1nh c\u1ee7a h\u00ecnh vu\u00f4ng \u0111\u00f3 r\u1ed3i t\u00ednh chu vi","explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai8/lv1/img\/H818_D1_9.jpg' \/><\/center> G\u1ecdi \u0111\u1ed9 d\u00e0i c\u1ea1nh c\u1ee7a h\u00ecnh vu\u00f4ng \u0111\u00f3 l\u00e0: $x\\, (cm)$ ($x > 0$) <br\/> Ta c\u00f3: $x^2+x^2=20^2$ (\u0111\u1ecbnh l\u00ed Pi - ta - go) <br\/> $\\Rightarrow 2x^2=20^2$ <br\/> $\\Rightarrow x^2=20^2:2=200$ <br\/> $\\Rightarrow x=10\\sqrt{2}\\, (cm)$ <br\/> Chu vi c\u1ee7a h\u00ecnh vu\u00f4ng \u0111\u00f3 l\u00e0: <br\/> $4.10\\sqrt{2}=40 \\sqrt{2}\\, (cm)$ <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 B. <\/span><\/span> ","column":4}]}],"id_ques":1509},{"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":" <span class='basic_left'> H\u00ecnh vu\u00f4ng c\u00f3 \u0111\u1ed9 d\u00e0i \u0111\u01b0\u1eddng ch\u00e9o l\u00e0 $24\\, cm$ th\u00ec di\u1ec7n t\u00edch c\u1ee7a h\u00ecnh vu\u00f4ng \u0111\u00f3 l\u00e0: <\/span>","select":[" A. $576\\, cm^2$"," B. $144\\, cm^2$","C. $288\\, cm^2$","D. $169\\, cm^2$"],"Hint":" T\u00ednh b\u00ecnh ph\u01b0\u01a1ng c\u1ee7a \u0111\u1ed9 d\u00e0i c\u1ea1nh h\u00ecnh vu\u00f4ng","explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai8/lv1/img\/H818_D1_9.jpg' \/><\/center> G\u1ecdi \u0111\u1ed9 d\u00e0i c\u1ea1nh c\u1ee7a h\u00ecnh vu\u00f4ng $ABCD$ theo b\u00e0i l\u00e0: $x \\, (cm)$ ($x > 0$) <br\/> $\\Rightarrow$ Di\u1ec7n t\u00edch h\u00ecnh vu\u00f4ng $ABCD$ \u0111\u00f3 l\u00e0: $x^2\\, (cm^2)$ <br\/> Ta \u0111i t\u00ecm gi\u00e1 tr\u1ecb c\u1ee7a $x^2$.<br\/> \u00c1p d\u1ee5ng \u0111\u1ecbnh l\u00ed Py - ta - go v\u00e0o $\\Delta ABD$ ta c\u00f3:<br\/> $x^2+x^2=24^2$ <br\/> $\\Rightarrow 2x^2=24^2$ <br\/> $\\Rightarrow x^2=24^2:2=288$ <br\/> Di\u1ec7n t\u00edch c\u1ee7a h\u00ecnh vu\u00f4ng $ABCD$ l\u00e0: $288\\, (cm^2)$. <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 C. <\/span><\/span> ","column":4}]}],"id_ques":1510}],"lesson":{"save":0,"level":1}}