cho tam giac ABC can tai A.tren cac canh ben AB,AClay theo thu tu cac điem D&E sao cho AD=AE

R

ronaldover7

tam giac ABC can tai A \Rightarrow góc B=C=$\frac{A}{2}$ (1)
AD=AE \Rightarrow tam giac ADE can tai A \Rightarrow góc D=E=$\frac{A}{2}$ (2)

(1)(2) \Rightarrow goc C=D=B=E

mà B,D đồng vị \Rightarrow DE//BC,D=B
\Rightarrow BDEC la hình thang cân
b/
goc C=D=B=E=$\frac{A}{2}$ ==$\frac{50^0}{2}$ =$25^0$
 
You must log in or register to reply here.
Top Bottom