\(\widehat{KAE}+\widehat{BAE}=90^0\)
\(\widehat{HAE}+\widehat{BEA}=90^0\)
mà \(\widehat{BAE}=\widehat{BEA}\)
nên \(\widehat{KAE}=\widehat{HAE}\)
Xét ΔKAE vuông tại K và ΔHAE vuông tại H có
AE chung
\(\widehat{KAE}=\widehat{HAE}\)
Do đó: ΔKAE=ΔHAE
Suy ra: AK=AH
Cho tam giac ABC vuong tai A, goc C=30do. Duong cao AH. Tren canh HC lay diem D sao cho HD=HB. Tu C keo CE vuong goc AD. Cm. a, Tam giac ABD deu. b, EH song song AC
Cho tam giac ABC biet AB nho hon AC.Tren tia BA lay diem D sao cho BC bang BD. Noi C voi D. Phan giac goc B cat canh AC ,DC tai E, I. Chung minh tam giac BEC bang tam giac BID .Tu A ve duong vuong goc voi DC , H thuoc DC.Chung minh AH song song voi BI
Cho tam giac deu ABC. Tren canh AB lay diem D sao cho AD=1/3 AB. Tu D ke duong thang vuong goc AB cat A o E, qua E ke duong thang vuong goc AC cat BC o F. Chung minh. a, DF vuong goc BC. b, Tam giac DEF la tam giac deu
Cho tam giac ABC ( AB<AC). Tren canh AB lay diem E sao cho AE=AD . Tia phan giac cua goc a cat canh BC tai D . Chung minh : a,tam giac ABD=tam giac AED b,DE=DB c, BE vuong goc voi AD
cho tam giac ABC co AB = AC . Tren canh BC lay D va tren tia doi cua BC lay E sao cho BD = BE . Cac duong thang vuong goc voi BC ke tu D va E cat AB ; AC lan luot tai M va N . Chung minh :
a/ DM=ED
b/duong thang BC cat MN tai diem I la trung diem cua MN
c/duong thang vuong goc voi MN tai I luon luon di qua mot diem co dinh khi D thay doi tren BC .
help me !!! 
1.cho tam giac ABC. tren tia doi cua tia BA lay diem D sao cho BD=BA. tren canh BC lay diem E sao cho BE =1/3 BC. goi K la giao diem cua AE va CD. chung minh rang DK=KC
2. cho tam giac ABC can tai A co AB =AC =5cm, BC=3cm. ke trung tuyen AM
a) chung minh AM vuong goc BC
b) tinh do dai AM
1. cho tam giac ABC. tren tia doi cua tia BA lay diem D sao cho BD=BA. tren canh BC lay diem E sao cho BE=\(\dfrac{1}{3}\)BC. goi K la giao diem cua AE va CD. Chung minh rang DK=KC
2. cho tam giac ABC can tai A co AB=AC=5cm,BC=3cm. ke trung tuyen AM
a. Chung minh rang AM vuong goc BC
b. tinh do dai AM
1cho hai tam giac vuong la abc va def co a=d=90 ,ac=df. hay bo sung them 1 dieu kien (ve canh hay ve goc ) de tam giac abc=tam giac def
2 cho tam giac abc can tai a (a<90) . ve bh vuong goc voi ac ( h thuoc ac) , ck vuong goc voi ab ( k thuoc ab)
a) chung minh ah=ak
b) goi i la giao diem cua bh va ck . chung minh rang ai la tia phan giac
3 tim cac cap tam giac bang nhau co tren hinh 131 sach vene 7
cho tam giac abc vuong tai a ( ab<ac) tia phan giac cua goc b cắt ac o d. ke dh vuong bc. tren tia ac lay diem e sao cho ae= ab. dg thanh vuong goc ab cat tia dh o k
