cho tam giac ABC vuong tai A , goc C =15 do tren tia BA lay O sao cho BO=2AC . chung minh rang tam giac OBC can
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cho tam giac ABC can tai A. tren tia doi cua tia BC lay diem M. tren tia doi cua tia CB lay diem N. sao cho BM bang CNa, chung minh tam giac AMN canb, ke BH vuong goc voi AM , CK vuong goc voi AN. chung minh rang BH bang CKc, chung minh AH bang AKd, goi O la giao diem cua HB va KC. tam giac OBC la tam giac gi? vi sao?e,khi goc BACbang 60 do ba BM bang CN bang BC. hay tinh so do cac goc cua tam giac AMN va xac dinh dang cua tam giac OBC (la loai gi vi sao)
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cho tam giac ABC can tai A. tren tia doi cua tia BC lay diem M. tren tia doi cua tia CB lay diem N. sao cho BM bang CN
a, chung minh tam giac AMN can
b, ke BH vuong goc voi AM , CK vuong goc voi AN. chung minh rang BH bang CK
c, chung minh AH bang AK
d, goi O la giao diem cua HB va KC. tam giac OBC la tam giac gi? vi sao?
e,khi goc BACbang 60 do ba BM bang CN bang BC. hay tinh so do cac goc cua tam giac AMN va xac dinh dang cua tam giac OBC (la loai gi vi sao)
cho tam giac ABC vuong tai B . Tia phan giac cua goc A cat canh BC tai D . Tren tia AC lay dien H sao cho AH= AB
a) chung minh rang tam giac AHD =tam giac ABD
b) chung minh rang DH vuong goc voi AC
cho tam giasc ABC can tai A tren tia doi cua tia BC lay diem D tren tia doi cua tia CB lay diem E sao cho BD=CE ke DH vuong goc voi AB ke EK vuong goc voi AC a,tam giac DAE la tam giac j | b,chung minh DH = EK| c,chung minh tam giac ADH =tam giac AEK | d,goi O la giao diem cua DH va EK chung minh tam giac DOE can | e, chung minh AO la phan giac cua goc DAE | g,goi I la trung diem cua BC chung minh rang ba diem A,I,O thang hang
cho tam giác abc cân tại a goc a 45 do tu trung diem I cua AC ve duong thang vuong goc voi Ac cat BC o M tren tia doi AM lay N sao cho AN=BM chung minh a, goc AMC=goc BAC b, tam giac ABM= tam giac CAN c, tam giac MNC vuong can tai C
Cho tam giac ABC vuong tai A. Tia phan giac cua goc ABC cat AC tai D, E la diem tren canh BC sao cho BE = BA. DE vuong goc voi BC
a) Chung minh rang tam giac ABD = tam giac EBD
b) Chung minh rang DE vuong goc voi BC
cho tam giac ABC vuong tai A ve phan giac cua goc ABC tia nay cat canh AC tai K tren canh BC lay diem D sao cho BD= BA a)chung minh KA=KD b)duong thang AB cat duong thang DK tai E chung minh tam giac KDC c) chung minh tam giac BEC can tai c
cho tam giac ABC. Goi M la trung diem BC va AM la tia phan giac cua goc A. Ve MI vuong goc AB, MH vuong goc AC. Chung minh rang:
a, MI = MH
b, Tam giac ABC can
c, Cho AB = 17 cm, AM = 15 cm. Tinh BC
d, Tren tia doi cua tia BC lay diem D, tren tia doi cua tia CB lay diem E sao cho BD = CE. Chung minh: tam giac AED can
cho tam giac abc can tai a co goc bac =50do tren tia doi cua tia bc lay diem d tren tia doi cua tia cb lay diem e sao cho bd =ba ce=ca tinh goc dae
cho tam giac abc deu ve ben ngoai tam giac cac tam giac abd vuong can tai b tam giac ace vuong can tai c tinh so goc nhon cua ade
XÉT \(\Delta ABC\)CÂN TẠI A
\(\Rightarrow\hept{\begin{cases}AB=AC\\\widehat{B}=\widehat{C}\end{cases}}\)
TA CÓ \(\widehat{A}+\widehat{B}+\widehat{C}=180^o\left(Đ/L\right)\)
THAY\(50^0+\widehat{B}+\widehat{C}=180^o\)
\(\widehat{B}+\widehat{C}=130^o\)
MÀ\(\widehat{B}=\widehat{C}\)
\(\Rightarrow\widehat{B}=\widehat{C}=\frac{130^o}{2}=65^o\)
TA CÓ \(\widehat{DBA}+\widehat{ABC}=180^o\left(KB\right)\)
\(\Rightarrow\widehat{DBA}=180^o-65^o=115^o\)
TA CÓ\(\widehat{ACE}+\widehat{ACB}=180^o\left(KB\right)\)
\(\Rightarrow\widehat{ACE}=180^o-65^0=115^o\)
XÉT \(\Delta ACE\)CÓ AC=CE (GT) =>\(\Delta ACE\)CÂN TẠI C
\(\Rightarrow\widehat{CAE}=\widehat{AEC}=\frac{180^o-115^0}{2}=32,5^0\)
XÉT \(\Delta ABD\)CÓ AB=BD (GT) =>\(\Delta ABD\)CÂN TẠI B
\(\Rightarrow\widehat{DAB}=\widehat{ADB}=\frac{180^o-115^0}{2}=32,5^0\)
TA CÓ\(\widehat{DAB}+\widehat{BAC}+\widehat{EAC}=\widehat{DAE}\)
THAY\(32,5^o+50^0+32,5^0=\widehat{DAE}\)
\(\Rightarrow\widehat{DAE}=115^0\)
cho tam giac ABC can tai A va goc A bang 30 do .Tren nua mat phang bo AB co chua diem C ve tia Bx vuong goc BA. Tren tia Bx lay diem N sao cho BN=BA .Tinh goc BCN