Question

The triangle ABC is isosceles (AB = AC)

DE parallel to BC
You need to prove: The ADE triangle is isosceles

Answer 1

ΔADE is isosceles

Explanation:

Δ ABC is isosceles

AB ≅ AC

∠B ≅ ∠C

If DE parallel to BC

AD ≅ AE

∠D ≅ ∠E

ΔADE is isosceles

The isosceles triangle is a polygon with three sides, two being equal and the other unequal.

The angles D and E will also be equal and the A other different.