Question

In an isosceles triangle, the vertex angle is double the sum of the degree measures of the base angles.

Answer 1

Answer:

Let △ABC be an isosceles triangle such that AB =AC  Then we have to prove that ∠B=∠C Draw the bisector AD of ∠A meeting BC in D 

Now in triangles ABD and ACD We have AB=AC (Given)

 ∠BAD=∠CAD (because AD is bisector of ∠A

AD=AD   (Common side)

Therefore by SAS congruence condition we have 

△ABC≅△ACD

⇒∠B=∠C

(Corresponding parts of congruent triangles are equal )