{"segment":[{"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'> Ch\u1ecdn kh\u1eb3ng \u0111\u1ecbnh sai trong c\u00e1c kh\u1eb3ng \u0111\u1ecbnh d\u01b0\u1edbi \u0111\u00e2y:<\/span>","select":["A. H\u00ecnh thoi c\u00f3 hai \u0111\u01b0\u1eddng ch\u00e9o b\u1eb1ng nhau","B. H\u00ecnh thoi c\u0169ng l\u00e0 h\u00ecnh b\u00ecnh h\u00e0nh","C. H\u00ecnh thoi l\u00e0 t\u1ee9 gi\u00e1c c\u00f3 b\u1ed1n c\u1ea1nh b\u1eb1ng nhau","D. H\u00ecnh thoi c\u00f3 hai \u0111\u01b0\u1eddng ch\u00e9o vu\u00f4ng g\u00f3c v\u1edbi nhau"],"explain":" <span class='basic_left'> C\u00e2u A sai <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 A. <\/span><\/span> ","column":1}]}],"id_ques":1461},{"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 thoi l\u00e0 t\u1ee9 gi\u00e1c: <\/span>","select":["A. C\u00f3 b\u1ed1n c\u1ea1nh b\u1eb1ng nhau","B. C\u00f3 b\u1ed1n g\u00f3c b\u1eb1ng nhau","C. C\u00f3 chi\u1ec1u d\u00e0i 2 \u0111\u01b0\u1eddng ch\u00e9o b\u1eb1ng nhau","D. C\u1ea3 ba \u0111\u00e1p \u00e1n tr\u00ean \u0111\u1ec1u \u0111\u00fang"],"explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai7/lv1/img\/H817_D1_1.jpg' \/><\/center> H\u00ecnh thoi c\u00f3 b\u1ed1n c\u1ea1nh b\u1eb1ng nhau <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 A. <\/span><\/span> ","column":2}]}],"id_ques":1462},{"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 b\u00ecnh h\u00e0nh l\u00e0 h\u00ecnh thoi khi: <\/span>","select":["A. C\u00f3 hai \u0111\u01b0\u1eddng ch\u00e9o vu\u00f4ng g\u00f3c","B. C\u00f3 hai \u0111\u01b0\u1eddng ch\u00e9o b\u1eb1ng nhau","C. C\u00f3 m\u1ed9t g\u00f3c vu\u00f4ng","D. C\u00f3 hai g\u00f3c \u0111\u1ed1i b\u1eb1ng nhau"],"explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai7/lv1/img\/H817_D2_2.jpg' \/><\/center> H\u00ecnh b\u00ecnh h\u00e0nh c\u00f3 hai \u0111\u01b0\u1eddng ch\u00e9o vu\u00f4ng g\u00f3c v\u1edbi nhau l\u00e0 h\u00ecnh thoi (d\u1ea5u hi\u1ec7u nh\u1eadn bi\u1ebft) <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 A. <\/span><\/span> ","column":2}]}],"id_ques":1463},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["DB"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<span class='basic_left'> Cho h\u00ecnh thoi $ABCD$ trong h\u00ecnh sau: <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai7/lv1/img\/H817_D2_1.jpg' \/><\/center> Ph\u00e2n gi\u00e1c c\u1ee7a $\\widehat{ADC}$ l\u00e0 \u0111\u01b0\u1eddng th\u1eb3ng _input_ <\/span> ","explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai7/lv1/img\/H817_D2_1.jpg' \/><\/center> Theo t\u00ednh ch\u1ea5t c\u1ee7a h\u00ecnh thoi, hai \u0111\u01b0\u1eddng ch\u00e9o l\u00e0 c\u00e1c ph\u00e2n gi\u00e1c c\u1ee7a c\u00e1c g\u00f3c trong h\u00ecnh thoi \u0111\u00f3. <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $DB$ <\/span> <\/span> "}]}],"id_ques":1464},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["25"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<span class='basic_left'> Cho h\u00ecnh thoi $ABCD$ trong h\u00ecnh sau <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai7/lv1/img\/H817_D1_2.jpg' \/><\/center> Bi\u1ebft $OA=24\\, cm; OB=7\\, cm$ <br\/> \u0110\u1ed9 d\u00e0i c\u1ea1nh h\u00ecnh thoi $ABCD$ l\u00e0 _input_ $(cm)$ <\/span> ","explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai7/lv1/img\/H817_D1_2.jpg' \/><\/center> Theo t\u00ednh ch\u1ea5t c\u1ee7a h\u00ecnh thoi: $AC\\bot BD$ <br\/> X\u00e9t tam gi\u00e1c vu\u00f4ng $ABO$ c\u00f3: <br\/> $AB^2=BO^2+AO^2$ (\u0111\u1ecbnh l\u00fd Pi - ta - go) <br\/> $AB^2=7^2+24^2=625$ <br\/> $\\Rightarrow AB=25\\, (cm)$ <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $25$ <\/span> <\/span> "}]}],"id_ques":1465},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["12"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<span class='basic_left'> Cho h\u00ecnh thoi $ABCD$ trong h\u00ecnh sau <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai7/lv1/img\/H817_D1_3.jpg' \/><\/center> Bi\u1ebft $OA=8\\, cm; AD=10\\, cm$ <br\/> \u0110\u1ed9 d\u00e0i \u0111\u01b0\u1eddng ch\u00e9o $BD$ l\u00e0 _input_ $(cm)$ <\/span> ","explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai7/lv1/img\/H817_D1_3.jpg' \/><\/center> Theo t\u00ednh ch\u1ea5t c\u1ee7a h\u00ecnh thoi: $AC\\bot BD$ <br\/> X\u00e9t tam gi\u00e1c vu\u00f4ng $ADO$ c\u00f3: <br\/> $ AO^2=DO^2+AO^2$ (\u0111\u1ecbnh l\u00fd Pi - ta - go) <br\/> $OD^2=AD^2-AO^2$ <br\/> $\\Rightarrow OD^2=10^2-8^2=36$ <br\/> $\\Rightarrow OD=6\\, cm$ <br\/> M\u00e0 $BD=2OB$ (t\u00ednh ch\u1ea5t h\u00ecnh thoi) <br\/> $\\Rightarrow BD=12\\, (cm)$ <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $12$ <\/span> <\/span> "}]}],"id_ques":1466},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["20"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<span class='basic_left'> Cho h\u00ecnh thoi $ABCD$ trong h\u00ecnh sau: <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai7/lv1/img\/H817_D2_1.jpg' \/><\/center> Bi\u1ebft $AC=32\\, cm; BD=24\\, cm$ <br\/> \u0110\u1ed9 d\u00e0i c\u1ea1nh c\u1ee7a h\u00ecnh thoi l\u00e0 _input_ (cm) <\/span> ","hint":" T\u00ednh \u0111\u1ed9 d\u00e0i $AB$ trong tam gi\u00e1c vu\u00f4ng $ABO$","explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai7/lv1/img\/H817_D2_1.jpg' \/><\/center> Theo t\u00ednh ch\u1ea5t c\u1ee7a h\u00ecnh thoi, ta c\u00f3: <br\/> $ AO=\\dfrac{AC}{2}=\\dfrac{32}{2}=16\\, (cm) $ <br\/> $BO=\\dfrac{BD}{2}=\\dfrac{24}{2}=12\\, (cm)$ <br\/> Do $AC\\bot BD$ (t\u00ednh ch\u1ea5t) $\\Rightarrow \\widehat{AOB}=90^o$ <br\/> X\u00e9t tam gi\u00e1c vu\u00f4ng $ABO$: <br\/> $ AB^2=BO^2+AO^2$ (\u0111\u1ecbnh l\u00fd Pi - ta - go) <br\/> $\\Rightarrow AB^2=12^2+16^2$ <br\/> $AB^2=400$ <br\/> $\\Rightarrow AB=20\\, cm$ <br\/> V\u1eady c\u1ea1nh c\u1ee7a h\u00ecnh thoi l\u00e0 $20 cm$ <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $20$ <\/span> <\/span> "}]}],"id_ques":1467},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["66"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<span class='basic_left'> Cho h\u00ecnh thoi $ABCD$ trong h\u00ecnh sau <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai7/lv1/img\/H817_D1_4.jpg' \/><\/center> Bi\u1ebft $\\widehat{OAD}=24^o$ <br\/> T\u00ednh $\\widehat{ABO}$. <br\/><br\/> <b> \u0110\u00e1p \u00e1n: <\/b> $\\widehat{ABO}=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}^o$ <\/span> ","explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai7/lv1/img\/H817_D1_4.jpg' \/><\/center> Theo t\u00ednh ch\u1ea5t c\u1ee7a h\u00ecnh thoi, ta c\u00f3: $\\widehat{OAD}=\\widehat{OAB}=24^o$ <br\/> $\\Rightarrow \\widehat{BAD}=48^o$ <br\/> M\u00e0 $AB=AD$ (t\u00ednh ch\u1ea5t h\u00ecnh thoi) <br\/> $\\Rightarrow \\Delta ABD$ c\u00e2n t\u1ea1i $A$ <br\/> $\\Rightarrow \\widehat{ABO}=\\widehat{ADO}=\\dfrac{180^o-48^o}{2}=66^o$ <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $66$ <\/span> <\/span> "}]}],"id_ques":1468},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["10"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<span class='basic_left'> Cho h\u00ecnh thoi $ABCD$ trong h\u00ecnh sau <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai7/lv1/img\/H817_D1_5.jpg' \/><\/center> Bi\u1ebft $\\widehat{ABO}=80^o$ <br\/> T\u00ednh $\\widehat{OAD}$. <br\/><br\/> <b> \u0110\u00e1p \u00e1n: <\/b> $\\widehat{OAD}=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}^o$ <\/span> ","explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai7/lv1/img\/H817_D1_5.jpg' \/><\/center> Theo t\u00ednh ch\u1ea5t c\u1ee7a h\u00ecnh thoi, ta c\u00f3: $AB=AD$ <br\/> $\\Rightarrow \\Delta ABD$ c\u00e2n t\u1ea1i $A$ <br\/> $\\Rightarrow \\widehat{ABO}=\\widehat{ADO}=80^o$ <br\/> X\u00e9t $\\Delta BAD$ c\u00f3: $2\\widehat{ABO}+\\widehat{BAD}=180^o$ <br\/> $\\Rightarrow \\widehat{BAD}=180^o-2.80^o=20^o$ <br\/> M\u00e0 $AO$ l\u00e0 ph\u00e2n gi\u00e1c c\u1ee7a g\u00f3c $BAD$ (t\u00ednh ch\u1ea5t h\u00ecnh thoi) <br\/> $\\Rightarrow \\widehat{BAO}=\\widehat{DAO}=\\dfrac{20^o}{2}=10^o$ <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $10$ <\/span> <\/span> "}]}],"id_ques":1469},{"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 $\\Delta ABC$, qua \u0111i\u1ec3m $D\\in BC$ k\u1ebb c\u00e1c \u0111\u01b0\u1eddng th\u1eb3ng song song v\u1edbi $AB$ v\u00e0 $AC$ c\u1eaft $AC, AB$ theo th\u1ee9 t\u1ef1 t\u1ea1i $E$ v\u00e0 $F$ <br\/> <b> C\u00e2u 1: <\/b> T\u1ee9 gi\u00e1c $AEDF$ l\u00e0 h\u00ecnh g\u00ec? <\/span>","select":["A. H\u00ecnh thoi","B. H\u00ecnh ch\u1eef nh\u1eadt","C. H\u00ecnh b\u00ecnh h\u00e0nh","D. H\u00ecnh thang"],"explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai7/lv1/img\/H817_D1_6.jpg' \/><\/center> Theo gi\u1ea3 thi\u1ebft \u0111\u00e3 cho th\u00ec $DE\/\/AB; DF\/\/AC$ <br\/> $\\Rightarrow DE\/\/AF; DF\/\/AE$ <br\/> $\\Rightarrow AEDF$ l\u00e0 h\u00ecnh b\u00ecnh h\u00e0nh (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":1470},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t <br\/> Kh\u1eb3ng \u0111\u1ecbnh sau \u0111\u00e2y \u0111\u00fang hay sai","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":5,"ques":" <span class='basic_left'> Cho $\\Delta ABC$, qua \u0111i\u1ec3m $D\\in BC$ k\u1ebb c\u00e1c \u0111\u01b0\u1eddng th\u1eb3ng song song v\u1edbi $AB$ v\u00e0 $AC$ c\u1eaft $AC, AB$ theo th\u1ee9 t\u1ef1 t\u1ea1i $E$ v\u00e0 $F$ <br\/> <b> C\u00e2u 2: <\/b> N\u1ebfu \u0111i\u1ec3m $D$ n\u1eb1m tr\u00ean tia ph\u00e2n gi\u00e1c c\u1ee7a g\u00f3c $A$ th\u00ec $AEDF$ l\u00e0 h\u00ecnh thoi. <\/span>","select":[" \u0110\u00fang"," Sai"],"explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai7/lv1/img\/H817_D1_6b.jpg' \/><\/center> Theo c\u00e2u 1, ta ch\u1ee9ng minh \u0111\u01b0\u1ee3c $AEDF$ l\u00e0 h\u00ecnh b\u00ecnh h\u00e0nh <br\/> N\u1ebfu $D$ n\u1eb1m tr\u00ean tia ph\u00e2n gi\u00e1c c\u1ee7a g\u00f3c $A$, t\u1ee9c l\u00e0 $AD$ l\u00e0 ph\u00e2n gi\u00e1c g\u00f3c $A$ th\u00ec $AEDF$ l\u00e0 h\u00ecnh thoi (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":1471},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"\u0110\u1ec1 chung cho hai c\u00e2u","temp":"fill_the_blank","correct":[[["="]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<span class='basic_left'> Cho h\u00ecnh thoi $ABCD$ c\u00f3 $\\widehat{A}=60^o$. K\u1ebb $BH\\bot AD; (H\\in AD)$, k\u00e9o d\u00e0i m\u1ed9t \u0111o\u1ea1n $HE=BH$. N\u1ed1i $E$ v\u1edbi $A, E$ v\u1edbi $D$ <br\/> <b> C\u00e2u 1: <\/b> So s\u00e1nh \u0111\u1ed9 d\u00e0i $AH$ v\u00e0 $DH$. <br\/><br\/> <b> \u0110\u00e1p \u00e1n: <\/b> $AH \\, \\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{} \\, DH$ <\/span> ","explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai7/lv1/img\/H817_D1_7.jpg' \/><\/center> Theo b\u00e0i, h\u00ecnh thoi $ABCD$ c\u00f3 $\\widehat{A}=60^o$ <br\/> $\\Rightarrow \\widehat{B}=120^o$ <br\/> M\u00e0 $BD$ l\u00e0 ph\u00e2n gi\u00e1c c\u1ee7a g\u00f3c $B$ n\u00ean $\\widehat{ABD}=\\widehat{DBC}=60^o$ <br\/> $\\Rightarrow \\Delta ABD$ \u0111\u1ec1u <br\/> L\u1ea1i c\u00f3: $BH\\bot AD (H\\in AD)$ <br\/> $\\Rightarrow AH=HD$ <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $=$ <\/span> <br\/> <b> L\u01b0u \u00fd: <\/b> <i> Trong tam gi\u00e1c \u0111\u1ec1u \u0111\u01b0\u1eddng cao xu\u1ea5t ph\u00e1t t\u1eeb m\u1ed9t \u0111\u1ec9nh c\u0169ng ch\u00ednh l\u00e0 \u0111\u01b0\u1eddng ph\u00e2n gi\u00e1c, \u0111\u01b0\u1eddng trung tuy\u1ebfn v\u00e0 \u0111\u01b0\u1eddng trung tr\u1ef1c. <\/i> <\/span> "}]}],"id_ques":1472},{"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 thoi $ABCD$ c\u00f3 $\\widehat{A}=60^o$. K\u1ebb $BH\\bot AD; (H\\in AD)$, k\u00e9o d\u00e0i m\u1ed9t \u0111o\u1ea1n $HE=BH$. N\u1ed1i $E$ v\u1edbi $A, E$ v\u1edbi $D$ <br\/> <b> C\u00e2u 2: <\/b> T\u1ee9 gi\u00e1c $ABDE$ l\u00e0 h\u00ecnh g\u00ec? <\/span>","select":["A. H\u00ecnh thoi","B. H\u00ecnh ch\u1eef nh\u1eadt","C. H\u00ecnh b\u00ecnh h\u00e0nh","D. H\u00ecnh thang"],"explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai7/lv1/img\/H817_D1_7.jpg' \/><\/center> Theo c\u00e2u 1, ta ch\u1ee9ng minh \u0111\u01b0\u1ee3c: $AH=DH$ (1) <br\/> H\u01a1n n\u1eefa: $EH=BH$ (gi\u1ea3 thi\u1ebft) (2) <br\/> M\u00e0 $BE\\cap AD=H$, do \u0111\u00f3 t\u1eeb (1) v\u00e0 (2) suy ra $ABDE$ l\u00e0 h\u00ecnh b\u00ecnh h\u00e0nh (hai \u0111\u01b0\u1eddng ch\u00e9o c\u1eaft nhau t\u1ea1i trung \u0111i\u1ec3m c\u1ee7a m\u1ed7i \u0111\u01b0\u1eddng) <br\/> M\u1eb7t kh\u00e1c: $BH\\bot AD \\Rightarrow BE\\bot AD$ <br\/> $\\Rightarrow $ $ABDE$ l\u00e0 h\u00ecnh thoi (h\u00ecnh b\u00ecnh h\u00e0nh c\u00f3 hai \u0111\u01b0\u1eddng ch\u00e9o vu\u00f4ng g\u00f3c) <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 A. <\/span><\/span> ","column":2}]}],"id_ques":1473},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"\u0110\u1ec1 chung cho b\u1ed1n c\u00e2u","temp":"multiple_choice","correct":[[2]],"list":[{"point":5,"ques":" <span class='basic_left'> Cho h\u00ecnh thoi $ABCD$ c\u00f3 $AB=BD=10\\, cm$. <br\/> <b> C\u00e2u 1: <\/b> Tam gi\u00e1c $ABD$ l\u00e0 tam gi\u00e1c g\u00ec? <\/span>","select":["A. Tam gi\u00e1c c\u00e2n","B. Tam gi\u00e1c \u0111\u1ec1u","C. Tam gi\u00e1c vu\u00f4ng","D. Tam gi\u00e1c vu\u00f4ng c\u00e2n"],"explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai7/lv1/img\/H817_D1_8.jpg' \/><\/center> Theo b\u00e0i $ABCD$ l\u00e0 h\u00ecnh thoi n\u00ean $AB = AD$ <br\/> M\u00e0 $AB=BD$ (gi\u1ea3 thi\u1ebft) <br\/> $\\Rightarrow AB = BD = AD$ <br\/> $\\Rightarrow \\Delta ABD$ l\u00e0 tam gi\u00e1c \u0111\u1ec1u <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 B <\/span><\/span> ","column":2}]}],"id_ques":1474},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"\u0110\u1ec1 chung cho b\u1ed1n c\u00e2u","temp":"fill_the_blank","correct":[[["60"],["120"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<span class='basic_left'> Cho h\u00ecnh thoi $ABCD$ c\u00f3 $AB=BD=10\\, cm$ <br\/> <b> C\u00e2u 2: <\/b> T\u00ednh c\u00e1c g\u00f3c c\u1ee7a h\u00ecnh thoi $ABCD$. <br\/><br\/> <b> \u0110\u00e1p \u00e1n: <\/b> <br\/> $\\widehat{A}=\\widehat{C}=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}^o$ <br\/> $\\widehat{B}=\\widehat{D}=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}^o$ <\/span> ","explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai7/lv1/img\/H817_D1_8.jpg' \/><\/center> Theo c\u00e2u 1, ta ch\u1ee9ng minh \u0111\u01b0\u1ee3c $\\Delta ABD$ l\u00e0 tam gi\u00e1c \u0111\u1ec1u <br\/> $\\Rightarrow \\widehat{BAD}=60^o$ <br\/> $\\Rightarrow \\widehat {BAD}=\\widehat{C}=60^o$ (t\u00ednh ch\u1ea5t h\u00ecnh thoi) <br\/> M\u00e0 $\\widehat{A}+\\widehat{B}=180^o$ <br\/> $\\Rightarrow \\widehat{B}=120^o$ <br\/> $\\Rightarrow \\widehat{D}=120^o$ <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u1ea7n l\u01b0\u1ee3t l\u00e0: $60$ v\u00e0 $120$ <\/span> <\/span> "}]}],"id_ques":1475},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"\u0110\u1ec1 chung cho b\u1ed1n c\u00e2u","temp":"fill_the_blank","correct":[[["10"],["3"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<span class='basic_left'> Cho h\u00ecnh thoi $ABCD$ c\u00f3 $AB=BD=10\\, cm$ <br\/> <b> C\u00e2u 3: <\/b> T\u00ednh \u0111\u1ed9 d\u00e0i $AC$. <br\/><br\/> <b> \u0110\u00e1p \u00e1n: <\/b> $AC=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}\\sqrt{\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}} \\, (cm)$ <\/span> ","hint":"X\u00e9t trong tam gi\u00e1c vu\u00f4ng $ABO$ \u0111\u1ec3 t\u00ecm $AO$ r\u1ed3i suy ra $AC$.","explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai7/lv1/img\/H817_D1_8.jpg' \/><\/center> G\u1ecdi $O=AC\\cap BD$ <br\/> Theo b\u00e0i cho: $BD=10\\, cm \\Rightarrow BO=\\dfrac{BD}{2}=\\dfrac{10}{2}=5\\, (cm)$ <br\/> X\u00e9t tam gi\u00e1c vu\u00f4ng $ABO$ c\u00f3: <br\/> $AB^2=AO^2+OB^2$ (\u0111\u1ecbnh l\u00fd Pi - ta - go) <br\/> $\\Rightarrow AO^2=AB^2-OB^2$ <br\/> $\\Rightarrow AO^2=10^2-5^2=75$ <br\/> $\\Rightarrow AO=5\\sqrt{3}\\, (cm)$ <br\/> M\u00e0: $AC=2AO$ (t\u00ednh ch\u1ea5t h\u00ecnh thoi) <br\/> $\\Rightarrow AC=10\\sqrt{3}\\, (cm)$ <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng \u0111\u1ec3 \u0111\u01b0\u1ee3c k\u1ebft qu\u1ea3 l\u00e0: $10\\sqrt{3}$ <\/span> <\/span> "}]}],"id_ques":1476},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"\u0110\u1ec1 chung cho b\u1ed1n c\u00e2u","temp":"fill_the_blank","correct":[[["50"],["3"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<span class='basic_left'> Cho h\u00ecnh thoi $ABCD$ c\u00f3 $AB=BD=10\\, cm$ <br\/> <b> C\u00e2u 4: <\/b> T\u00ednh di\u1ec7n t\u00edch h\u00ecnh thoi $ABCD$. <br\/><br\/> <b> \u0110\u00e1p \u00e1n: <\/b> $S_{ABCD}=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}\\sqrt{\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}} \\, (cm^2)$ <\/span> ","hint":"Di\u1ec7n t\u00edch h\u00ecnh thoi b\u1eb1ng n\u1eeda t\u00edch hai \u0111\u01b0\u1eddng ch\u00e9o","explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai7/lv1/img\/H817_D1_8.jpg' \/><\/center> G\u1ecdi $O=AC\\cap BD$ <br\/> Theo b\u00e0i cho: $BD=10\\, cm $ <br\/> Theo c\u00e2u 3, ta t\u00ednh \u0111\u01b0\u1ee3c: $ AC=10\\sqrt{3}\\, cm$ <br\/> Di\u1ec7n t\u00edch h\u00ecnh thoi $ABCD$ l\u00e0: <br\/> $\\dfrac{1}{2}AC.BD=\\dfrac{1}{2}.10\\sqrt{3}.10 = 50\\sqrt{3}\\, (cm^2)$ <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng \u0111\u1ec3 \u0111\u01b0\u1ee3c k\u1ebft qu\u1ea3 l\u00e0: $50\\sqrt{3}$ <\/span> <\/span> "}]}],"id_ques":1477},{"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":[[["13"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<span class='basic_left'> Cho h\u00ecnh thoi $ABCD$ c\u00f3 $AC=24\\, cm; BD=10\\, cm$. Bi\u1ebft $AC\\cap BD=O$ <br\/> <b> C\u00e2u 1: <\/b> T\u00ednh \u0111\u1ed9 d\u00e0i $AB$. <br\/><br\/> <b> \u0110\u00e1p \u00e1n: <\/b> $AB=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}\\, (cm)$ <\/span> ","explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai7/lv1/img\/H817_D1_8.jpg' \/><\/center> Theo t\u00ednh ch\u1ea5t h\u00ecnh thoi: <br\/> $AC=24\\, cm \\Rightarrow AO=12\\, (cm)$ <br\/> $BD=10\\, cm \\Rightarrow BO=5\\, (cm)$ <br\/> X\u00e9t tam gi\u00e1c vu\u00f4ng $ABO$ c\u00f3: <br\/> $AB^2=AO^2+BO^2$ (\u0111\u1ecbnh l\u00fd Pi - ta - go) <br\/> $\\Rightarrow AB^2=12^2+5^2=169$ <br\/> $\\Rightarrow AB=13\\, (cm)$ <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $13$ <\/span> <\/span> "}]}],"id_ques":1478},{"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":[[["52"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<span class='basic_left'> Cho h\u00ecnh thoi $ABCD$ c\u00f3 $AC=24\\, cm; BD=10\\, cm$. Bi\u1ebft $AC\\cap BD=O$ <br\/> <b> C\u00e2u 2: <\/b> T\u00ednh chu vi h\u00ecnh thoi $ABCD$. <br\/><br\/> <b> \u0110\u00e1p \u00e1n: <\/b> <br\/> Chu vi h\u00ecnh thoi l\u00e0 $\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}\\, (cm)$ <\/span> ","explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai7/lv1/img\/H817_D1_8.jpg' \/><\/center> Theo c\u00e2u 1, ta t\u00ednh \u0111\u01b0\u1ee3c: $AB=13\\, cm$ <br\/> Chu vi h\u00ecnh thoi l\u00e0: $4.13=52\\, (cm)$ <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $52$ <\/span> <\/span> "}]}],"id_ques":1479},{"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":[[["120"]]],"list":[{"point":5,"width":40,"type_input":"","ques":"<span class='basic_left'> Cho h\u00ecnh thoi $ABCD$ c\u00f3 $AC=24\\, cm; BD=10\\, cm$. Bi\u1ebft $AC\\cap BD=O$ <br\/> <b> C\u00e2u 3: <\/b> T\u00ednh di\u1ec7n t\u00edch h\u00ecnh thoi $ABCD$. <br\/><br\/> <b> \u0110\u00e1p \u00e1n: <\/b> $S_{ABCD}=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{} \\, (cm^2)$ <\/span> ","hint":"Di\u1ec7n t\u00edch h\u00ecnh thoi b\u1eb1ng n\u1eeda t\u00edch hai \u0111\u01b0\u1eddng ch\u00e9o","explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai7/lv1/img\/H817_D1_8.jpg' \/><\/center> Theo b\u00e0i cho: $BD=10\\, cm ; AC=24\\, (cm)$ <br\/> Di\u1ec7n t\u00edch h\u00ecnh thoi $ABCD$ l\u00e0: <br\/> $\\dfrac{1}{2}AC.BD=\\dfrac{1}{2}.24.10=120\\, (cm^2)$ <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng \u0111\u1ec3 \u0111\u01b0\u1ee3c k\u1ebft qu\u1ea3 l\u00e0: $120\\, (cm^2)$ <\/span> <\/span> "}]}],"id_ques":1480}],"lesson":{"save":0,"level":1}}