Bai 2:cho \(\Delta ABC\) co AB=AC;M la trung diem BC
a/ chung minh \(\Delta AMB=\Delta AMC\)
b/ Chung minh \(AM\perp BC\)
c/\(\Delta ABC\)co goc A=\(^{40^o}\). Tinh goc B
Bai 3: Cho \(\Delta ABC\)vuong tai A, lay D thuoc canh BC sao cho BD=BA; tia phan giac go B cat canh AC o E
a/ Chung minh \(\Delta ABE=\Delta DBE\)
b/ Chung minh goc BEA= goc BED.
c/ Ve tia \(Ex\perp BE\)tai E. Chung minh Ex / / AD
Bai 4: Cho \(\Delta ABC\)co AB= AC, H la trung diem BC
a/ Chung minh \(\Delta ABH=\Delta ACH\)
b/ Tren canh AB lay diem M, tren canh AC lay diem N sao cho MA=AN
c/ Goi E la giao diem cua AH va MN. Chung minh \(\Delta AME=\Delta ANE\)
d/ Chung minh MN / / BC
Moi ng giup em vs ak. E dang can gap lam. Ai lam dung va nhanh nhat e se tick cho ak. tks mn nhieu. <3
