{"segment":[{"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[4]],"list":[{"point":10,"ques":"T\u1ed5ng ba g\u00f3c trong m\u1ed9t tam gi\u00e1c b\u1eb1ng:","select":["A. $90^o$","B. $120^o$","C. $45^o$","D. $180^o$"],"hint":"","explain":" <span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/> Theo \u0111\u1ecbnh l\u00fd t\u1ed5ng 3 g\u00f3c trong m\u1ed9t tam gi\u00e1c: T\u1ed5ng ba g\u00f3c trong m\u1ed9t tam gi\u00e1c b\u1eb1ng $180^o$ <br\/><span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0: D<\/span> ","column":2}],"id_ques":1791},{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":10,"ques":"$\\triangle{MNP}$ vu\u00f4ng t\u1ea1i $P$ v\u00e0 c\u00f3 $\\hat{M}=28^o$. S\u1ed1 \u0111o g\u00f3c $N$ l\u00e0: ","select":["A. $45^o$","B. $135^o$","C. $62^o$","D. $72^o$"],"hint":"D\u1ef1a v\u00e0o \u0111\u1ecbnh l\u00fd t\u1ed5ng $3$ g\u00f3c trong m\u1ed9t tam gi\u00e1c","explain":" <span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/> $\\triangle{MNP}$ c\u00f3: <br\/> $\\begin{cases} \\widehat{P} = 90^o (gt) \\\\ \\widehat{M}=28^o (gt) \\end{cases}$ <br\/> $\\widehat{M} + \\widehat{N} + \\widehat{P} = 180^o$ (\u0111\u1ecbnh l\u00fd t\u1ed5ng 3 g\u00f3c trong m\u1ed9t tam gi\u00e1c) <br\/> $\\begin{align} \\Rightarrow \\widehat{N} &=180^o-\\widehat{P}-\\widehat{M} \\\\ \\widehat{N}&=180^o - 90^o - 28^o \\\\ \\widehat{N}&={{62}^{o}} \\end{align} $ <br\/><span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0: C<\/span> ","column":2}],"id_ques":1792},{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":10,"ques":"$\\triangle{ABC}$ c\u00e2n t\u1ea1i $A$ c\u00f3 s\u1ed1 \u0111o g\u00f3c $C$ b\u1eb1ng $32^{o}$. S\u1ed1 \u0111o g\u00f3c $A$ l\u00e0: ","select":["A. $32^o$","B. $58^o$","C. $116^o$","D. $148^o$"],"hint":"D\u1ef1a v\u00e0o \u0111\u1ecbnh l\u00fd t\u1ed5ng $3$ g\u00f3c trong m\u1ed9t tam gi\u00e1c v\u00e0 \u0111\u1ecbnh ngh\u0129a tam gi\u00e1c c\u00e2n","explain":" <span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/> $\\triangle{ABC}$ c\u00e2n t\u1ea1i $A$ $\\Rightarrow \\widehat{B}=\\widehat{C}=32^{o}$ <br\/> Theo \u0111\u1ecbnh l\u00fd t\u1ed5ng 3 g\u00f3c trong tam gi\u00e1c ta c\u00f3: <br\/> $\\begin{align} & \\widehat{A}+\\widehat{B}+\\widehat{C}=180^{o} \\\\ & \\widehat{A} + 32^{o} + 32^{o}=180^{o} \\\\ & \\widehat{A}=180^{o} - 64^{o} \\\\ & \\widehat{A} = 116^{o} \\end{align}$ <br\/><span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0: C <\/span> ","column":2}],"id_ques":1793},{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":10,"ques":"$\\triangle{HIK}$ vu\u00f4ng t\u1ea1i $H$ c\u00f3 \u0111\u1ed9 d\u00e0i c\u1ea1nh $HI = 12cm$, \u0111\u1ed9 d\u00e0i c\u1ea1nh $HK = 9cm$. \u0110\u1ed9 d\u00e0i c\u1ea1nh huy\u1ec1n $IK$ l\u00e0: ","select":["A. $15cm$","B. $14cm$","C. $16cm$","D. $20cm$"],"hint":"\u00c1p d\u1ee5ng \u0111\u1ecbnh l\u00fd Pitago","explain":" <span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/> \u00c1p d\u1ee5ng \u0111\u1ecbnh l\u00fd Pitago cho tam gi\u00e1c vu\u00f4ng $HIK$ ta c\u00f3: <br\/> $\\begin{align} HI^2+HK^2 &= IK^2 \\\\ 12^2+9^2&=IK^2 \\\\ IK^2 &=225 \\\\ \\Rightarrow IK=15(cm) \\end{align}$ <br\/><span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0: A <\/span> ","column":2}],"id_ques":1794},{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":10,"ques":"Trong c\u00e1c tam gi\u00e1c c\u00f3 c\u00e1c k\u00edch th\u01b0\u1edbc sau \u0111\u00e2y, tam gi\u00e1c n\u00e0o l\u00e0 tam gi\u00e1c vu\u00f4ng? ","select":["A. $3cm; 5cm; 7cm$ ","B. $3cm; 4cm; 5cm$ ","C. $9cm; 10cm; 12cm$ ","D. $8cm; 10cm; 15cm$ "],"hint":"D\u1ef1a v\u00e0o \u0111\u1ecbnh l\u00fd \u0111\u1ea3o c\u1ee7a \u0111\u1ecbnh l\u00fd Pitago","explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> T\u00ednh t\u1ed5ng hai b\u00ecnh ph\u01b0\u01a1ng c\u1ee7a \u0111\u1ed9 d\u00e0i hai c\u1ea1nh nh\u1ecf h\u01a1n v\u00e0 so s\u00e1nh v\u1edbi b\u00ecnh ph\u01b0\u01a1ng \u0111\u1ed9 d\u00e0i c\u1ea1nh l\u1edbn nh\u1ea5t <br\/><br\/> <span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/> A. $3^{2} + 5^2 = 34 \\neq 49 = 7^2$ <br\/> $\\Rightarrow $ Tam gi\u00e1c c\u00f3 k\u00edch th\u01b0\u1edbc nh\u01b0 tr\u00ean kh\u00f4ng ph\u1ea3i tam gi\u00e1c vu\u00f4ng (theo \u0111\u1ecbnh l\u00fd \u0111\u1ea3o c\u1ee7a \u0111\u1ecbnh l\u00fd Pitago) <br\/> B. $3^2 + 4^2 = 25 = 5^2$ <br\/> $\\Rightarrow $ Tam gi\u00e1c c\u00f3 k\u00edch th\u01b0\u1edbc nh\u01b0 tr\u00ean l\u00e0 tam gi\u00e1c vu\u00f4ng (theo \u0111\u1ecbnh l\u00fd \u0111\u1ea3o c\u1ee7a \u0111\u1ecbnh l\u00fd Pitago) <br\/> C. $9^2 + 10^2 = 181 \\neq 144 = 12^2$ <br\/> $\\Rightarrow $ Tam gi\u00e1c c\u00f3 k\u00edch th\u01b0\u1edbc nh\u01b0 tr\u00ean kh\u00f4ng ph\u1ea3i l\u00e0 tam gi\u00e1c vu\u00f4ng (theo \u0111\u1ecbnh l\u00fd \u0111\u1ea3o c\u1ee7a \u0111\u1ecbnh l\u00fd Pitago) <br\/> D. $8^2 + 10^2 = 164 \\neq 225 = 15^2$ <br\/> $\\Rightarrow $ Tam gi\u00e1c c\u00f3 k\u00edch th\u01b0\u1edbc nh\u01b0 tr\u00ean kh\u00f4ng ph\u1ea3i l\u00e0 tam gi\u00e1c vu\u00f4ng (theo \u0111\u1ecbnh l\u00fd \u0111\u1ea3o c\u1ee7a \u0111\u1ecbnh l\u00fd Pitago) <br\/><span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0: B <\/span> ","column":2}],"id_ques":1795},{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":10,"ques":"Tam gi\u00e1c $ABC$ v\u00e0 tam gi\u00e1c $MNP$ c\u00f3 $AB = MN$; $AC = MP$. C\u1ea7n th\u00eam \u0111i\u1ec1u ki\u1ec7n n\u00e0o sau \u0111\u00e2y \u0111\u1ec3 $\\triangle{ABC}=\\triangle{MNP}$?","select":["A. $\\widehat{A}=\\widehat{M}$ ","B. $\\widehat{C}=\\widehat{P}$ ","C. $NP = AB $ ","D. $\\widehat{B}=\\widehat{N}$ "],"hint":"V\u1ebd h\u00ecnh, d\u1ef1a v\u00e0o c\u00e1c tr\u01b0\u1eddng h\u1ee3p b\u1eb1ng nhau c\u1ee7a hai tam gi\u00e1c","explain":" <span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/> Theo \u0111\u1ec1 b\u00e0i ta c\u00f3 h\u00ecnh v\u1ebd: <br\/> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop7/toan/hinhhoc/H7kiemtrachuong2/lv3/img\/H7kiemtrachuong2_07.png' \/><\/center> <br\/> X\u00e9t $\\triangle{ABC}$ v\u00e0 $\\triangle{MNP}$ c\u00f3: <br\/> $AB = MN (gt)$ <br\/> $AC = MP (gt)$ <br\/> N\u1ebfu c\u00f3: $\\widehat{A} = \\widehat{M}$ <br\/> $\\Rightarrow \\triangle{ABC} = \\triangle{MNP}$ (c.g.c) <br\/> N\u1ebfu c\u00f3: $BC = NP$ <br\/> $\\Rightarrow \\triangle{ABC} = \\triangle{MNP}$ (c.c.c) <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0: A <\/span> ","column":2}],"id_ques":1796},{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":10,"ques":"Cho tam gi\u00e1c $ABC$. K\u1ebb $DE$ song song v\u1edbi $BC$ v\u00e0 s\u1ed1 \u0111o c\u00e1c g\u00f3c nh\u01b0 h\u00ecnh v\u1ebd: <br\/> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop7/toan/hinhhoc/H7kiemtrachuong2/lv3/img\/H7kiemtrachuong2_01.png' \/><\/center> <br\/> S\u1ed1 \u0111o $\\widehat{BAC}$ l\u00e0:","select":["A. $60^{o}$ ","B. $70^{o}$ ","C. $80^{o} $ ","D. $90^{o}$ "],"hint":"D\u1ef1a v\u00e0o t\u00ednh ch\u1ea5t g\u00f3c ngo\u00e0i c\u1ee7a tam gi\u00e1c","explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> <b> B\u01b0\u1edbc 1: <\/b> T\u00ednh s\u1ed1 \u0111o g\u00f3c $C$ <br\/> <b> B\u01b0\u1edbc 2: <\/b> D\u1ef1a v\u00e0o t\u00ednh ch\u1ea5t g\u00f3c ngo\u00e0i c\u1ee7a tam gi\u00e1c \u0111\u1ec3 t\u00ednh s\u1ed1 \u0111o g\u00f3c $\\widehat{BAC}$ <br\/><br\/> <span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop7/toan/hinhhoc/H7kiemtrachuong2/lv3/img\/H7kiemtrachuong2_01.png' \/><\/center> <br\/> G\u00f3c $\\widehat{ABx}$ l\u00e0 g\u00f3c ngo\u00e0i c\u1ee7a tam gi\u00e1c $ABC$ <br\/> $\\Rightarrow \\widehat{ABx}=\\widehat{A}+\\widehat{C}$ (t\u00ednh ch\u1ea5t g\u00f3c ngo\u00e0i c\u1ee7a tam gi\u00e1c) (1) <br\/> Ta c\u00f3: $ DE \/\/ BC$ (gt) <br\/> $\\Rightarrow \\widehat{C} = \\widehat{AED} = 50^{o}$ (\u0111\u1ed3ng v\u1ecb) (2) <br\/> T\u1eeb (1) v\u00e0 (2) <br\/> $\\begin{align} \\Rightarrow \\widehat{ABx} &= \\widehat{A}+50^{o} \\\\ 120^{o} &=\\widehat{A}+50^{o} \\\\ \\widehat{A} &=70^{o} \\end{align}$ <br\/> Hay $\\widehat{BAC}=70^{o}$ <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0: B <\/span> ","column":2}],"id_ques":1797},{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[4]],"list":[{"point":10,"ques":"Ph\u00e1t bi\u1ec3u n\u00e0o sau \u0111\u00e2y \u0111\u00fang? ","select":["<span class='basic_left'> A. Hai tam gi\u00e1c c\u00f3 hai c\u1ea1nh b\u1eb1ng nhau \u0111\u00f4i m\u1ed9t v\u00e0 m\u1ed9t g\u00f3c b\u1eb1ng nhau th\u00ec b\u1eb1ng nhau <\/span>"," <span class='basic_left'>B. Hai tam gi\u00e1c c\u00f3 m\u1ed9t c\u1ea1nh b\u1eb1ng nhau v\u00e0 hai g\u00f3c b\u1eb1ng nhau th\u00ec b\u1eb1ng nhau <\/span> ","<span class='basic_left'>C. Hai tam gi\u00e1c vu\u00f4ng c\u00f3 m\u1ed9t g\u00f3c vu\u00f4ng b\u1eb1ng nhau v\u00e0 m\u1ed9t g\u00f3c nh\u1ecdn b\u1eb1ng nhau th\u00ec b\u1eb1ng nhau <\/span> "," <span class='basic_left'> D. Hai tam gi\u00e1c vu\u00f4ng c\u00f3 hai c\u1ea1nh g\u00f3c vu\u00f4ng c\u1ee7a tam gi\u00e1c vu\u00f4ng n\u00e0y l\u1ea7n l\u01b0\u1ee3t b\u1eb1ng hai c\u1ea1nh g\u00f3c vu\u00f4ng c\u1ee7a tam gi\u00e1c vu\u00f4ng kia th\u00ec ch\u00fang b\u1eb1ng nhau. <\/span> "],"hint":"","explain":" <span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/> C\u00e2u A sai v\u00ec: <br\/> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop7/toan/hinhhoc/H7kiemtrachuong2/lv3/img\/H7kiemtrachuong2_03.png' \/><\/center> <br\/> C\u00e2u B sai v\u00ec: <br\/> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop7/toan/hinhhoc/H7kiemtrachuong2/lv3/img\/H7kiemtrachuong2_04.png' \/><\/center> <br\/> C\u00e2u C sai v\u00ec: <br\/> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop7/toan/hinhhoc/H7kiemtrachuong2/lv3/img\/H7kiemtrachuong2_05.png' \/><\/center> <br\/> C\u00e2u D \u0111\u00fang v\u00ec: <br\/> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop7/toan/hinhhoc/H7kiemtrachuong2/lv3/img\/H7kiemtrachuong2_06.png' \/><\/center> <br\/> $\\triangle{MNP}$ v\u00e0 $\\triangle{GIH}$ c\u00f3: <br\/> $MN=GI$ (gt) <br\/> $\\widehat{M} = \\widehat{G} = 90^{o}$ <br\/> $MP=GH$ (gt) <br\/> $\\Rightarrow \\triangle{MNP} =\\triangle{GIH}$ (c.g.c) <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0: D <\/span> ","column":1}],"id_ques":1798},{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":10,"ques":"Cho tam gi\u00e1c $ABC$ vu\u00f4ng t\u1ea1i $A$ c\u00f3 $\\widehat{B} = 60^o$ v\u00e0 $AB = 5cm$. Tia ph\u00e2n gi\u00e1c c\u1ee7a g\u00f3c $B$ c\u1eaft $AC$ t\u1ea1i $D$. K\u1ebb $DE$ vu\u00f4ng g\u00f3c v\u1edbi $BC$ t\u1ea1i $E$. T\u00ednh \u0111\u1ed9 d\u00e0i c\u1ea1nh $BC$.","select":["A. $7cm$ ","B. $10cm$ ","C. $8cm$ ","D. $12cm$ "],"hint":"T\u00ednh $BE, EC$ r\u1ed3i t\u00ednh $BC$ ","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 $\\triangle{ABD} = \\triangle{EBD}$ <br\/> <b> B\u01b0\u1edbc 2: <\/b> T\u00ednh $BE$ b\u1eb1ng c\u00e1ch ch\u1ee9ng minh $\\triangle{ABE}$ \u0111\u1ec1u <br\/> <b> B\u01b0\u1edbc 3: <\/b> T\u00ednh \u0111\u1ed9 d\u00e0i $EC$ r\u1ed3i t\u00ednh $BC = BE + EC$ <br\/><br\/> <span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop7/toan/hinhhoc/H7kiemtrachuong2/lv3/img\/H7kiemtrachuong2_08.png' \/><\/center> <br\/> X\u00e9t $\\triangle{ABD}$ v\u00e0 $\\triangle{EBD}$ c\u00f3: <br\/> $\\begin{cases} \\widehat{BAD} = \\widehat{BED} = 90^{o} \\text{(gt)} \\\\ BD \\hspace{0,2cm} \\text{l\u00e0} \\hspace{0,2cm} \\text{c\u1ea1nh} \\hspace{0,2cm} \\text{huy\u1ec1n} \\hspace{0,2cm} \\text{chung} \\\\ \\widehat{ABD} = \\widehat{EBD} \\text{(gt)} \\end{cases}$ <br\/> $\\Rightarrow \\triangle{ABD} = \\triangle{EBD}$ (c\u1ea1nh huy\u1ec1n \u2013 g\u00f3c nh\u1ecdn) <br\/> $\\Rightarrow AB = BE$ (c\u1ea1nh t\u01b0\u01a1ng \u1ee9ng) <br\/> $\\triangle{ABE}$ c\u00f3 $AB = BE$ v\u00e0 $\\widehat{B}=60^{0}$ n\u00ean $\\triangle{ABE}$ \u0111\u1ec1u. <br\/> $\\Rightarrow \\widehat{BAE}=\\widehat{BEA}=\\widehat{B}=60^o$ (t\u00ednh ch\u1ea5t tam gi\u00e1c \u0111\u1ec1u) (1) <br\/> $BE = AB = 5cm$ <br\/> M\u1eb7t kh\u00e1c: $\\widehat{EAC} + \\widehat{BAE} = 90^{o}$ (2) <br\/> $\\widehat{C} + \\widehat{B} = 90^{o}$ ($\\triangle ABC$ vu\u00f4ng t\u1ea1i $A$) (3) <br\/> T\u1eeb (1), (2), (3) $\\Rightarrow $ $\\widehat{EAC}=\\widehat{C}$ <br\/> $\\Rightarrow $ $\\triangle{AEC}$ c\u00e2n t\u1ea1i E (t\u00ednh ch\u1ea5t tam gi\u00e1c c\u00e2n) <br\/> $\\Rightarrow EA = EC$ (\u0111\u1ecbnh ngh\u0129a tam gi\u00e1c c\u00e2n) <br\/> M\u00e0 $EA = AB = EB = 5cm$ ($\\triangle{ABE}$ \u0111\u1ec1u) <br\/> Do \u0111\u00f3 $EC = 5cm$ <br\/> V\u1eady $BC = BE + EC = 5cm + 5cm = 10cm$ <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0: B. $10cm$ <\/span> ","column":2}],"id_ques":1799},{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":10,"ques":"Cho h\u00ecnh v\u1ebd: <br\/> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop7/toan/hinhhoc/H7kiemtrachuong2/lv3/img\/H7kiemtrachuong2_02.png' \/><\/center> <br\/> S\u1ed1 \u0111o $\\widehat{B_{1}} + \\widehat{C_{1}}$ l\u00e0: ","select":["A. $50^{o}$ ","B. $60^{o}$ ","C. $70^{o}$ ","D. $80^{o}$ "],"hint":"","explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> <b> B\u01b0\u1edbc 1: <\/b> T\u00ednh s\u1ed1 \u0111o $\\widehat{B}+\\widehat{C}$ d\u1ef1a v\u00e0o \u0111\u1ecbnh l\u00fd t\u1ed5ng 3 g\u00f3c <br\/> <b> B\u01b0\u1edbc 2: <\/b> T\u00ednh s\u1ed1 \u0111o $\\widehat{B_{2}}$ ; $\\widehat{C_{2}}$ <br\/> <b> B\u01b0\u1edbc 3: <\/b> T\u00ednh s\u1ed1 \u0111o $\\widehat{B_{1}} + \\widehat{C_{1}} = \\widehat{B}+\\widehat{C} - (\\widehat{B_{2}} + \\widehat{C_{2}}) $ <br\/><br\/> <span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop7/toan/hinhhoc/H7kiemtrachuong2/lv3/img\/H7kiemtrachuong2_02.png' \/><\/center> <br\/> $\\triangle{ABC}$ c\u00f3: $\\widehat{A} + \\widehat{B} + \\widehat{C} = 180^{o}$ (t\u1ed5ng 3 g\u00f3c trong m\u1ed9t tam gi\u00e1c) <br\/> $\\Rightarrow \\widehat{B}+\\widehat{C} = 180^{o} - \\widehat{A} = 180^{o} - 70^{o} = 110^{o}$ (1) <br\/> X\u00e9t tam gi\u00e1c $AIB$ c\u00f3: <br\/> $\\widehat{AIB}= 90^{o}$ (gt) <br\/> $\\widehat{AIB} + \\widehat{A} + \\widehat{B_{2}} = 180^{o}$ (t\u1ed5ng $3$ g\u00f3c trong $1$ tam gi\u00e1c) <br\/> $\\Rightarrow \\widehat{B_{2}} = 180^{o} - 70^{o} - 90^{o}$ <br\/> $\\widehat{B_{2}} = 20^{o}$ (2) <br\/> $\\Rightarrow \\widehat{C_{2}} = \\widehat{B_{2}} = 20^{o}$ (c\u00f9ng ph\u1ee5 v\u1edbi g\u00f3c $A$) (3) <br\/> M\u1eb7t kh\u00e1c ta c\u00f3: $\\widehat{B_{1}} + \\widehat{B_{2}} + \\widehat{C_{1}} + \\widehat{C_{2}} = \\widehat{B} + \\widehat{C}$ (4) <br\/> T\u1eeb (1), (2), (3), (4) <br\/> $\\begin{align} \\Rightarrow \\widehat{B_{1}} + \\widehat{C_{1}} &= \\widehat{B} + \\widehat{C} - (\\widehat{B_{2}} + \\widehat{C_{2}}) \\\\ &= 110^{o} - (20^{o} + 20^{o}) \\\\ & = 70^{o} \\end{align}$ <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0: C. $70^{o}$ <\/span>","column":2}],"id_ques":1800}],"id_ques":0}],"lesson":{"save":1,"level":3,"time":44}}