Bai 1: Tren duong thang AB lay diem O. Tren nua mat phang bo AB ve 2 tia OC va OD sao cho \(\widehat{AOC}=\widehat{BOD}=60^0\)

a, Hoi \(\widehat{AOC}\) va \(\widehat{BOD}\)co la 2 goc doi dinh khong? Vi sao?

b, Tren nua mat phang bo AB khong chua tia OD.Ve tia OE sao cho OB la tia phan giac cua \(\widehat{DOE}\). Hoi \(AOC\) va \(\widehat{BOE}\) co la 2 goc doi dinh khong? Vi sao?

Bai 2: 2 duong thang xx phay cat yy phay tai A sao cho \(\widehat{xAy}=47^0\). Tinh 3 goc con lai.

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

♡♡cho tam giac ABC can tai A . Gs O la giao diem cua AC vs AH . Lay E , F theo thu tu tren AB va AC sao cho AE = AF 

a) c/m : O cach deu 3 dinh cua tam giac ABC 

b) c/m : goc OCF = \(\frac{1}{2}\)goc BAC va tam giac OAE  = tam giac OCF

c) Neu tam giac ABC la tam giac bat ki . Lay M , N theo thu tu thuoc canh AB , AC sao cho AM = CN . Gs O la giao diem phan giac goc A va trung truc canh AC . c/m : trung truc cua MN di qua diem O .

    Bai nay hoi dai mong m.n giup mk .... ♡♡♡♥♥♥:-):-):-)