Question

Draw verticle angle of an isosceles triangle is 100degree.Find his base angles.

Answer 1

ANSWER WITH FULL EXPLANATION

Let the measure of each of the base angles be x°. 

Now, 
         [ Angle sum property of triangle. ]
⇒ (for these steps check this attachment)
⇒
⇒
⇒

∴ The measure of each of the base angles of the triangle is 40°. 

Hope this may help you. 

If you have any doubt, then you can ask me in the comments. 

Answer 2

angle sum property of a triangle =180

one angle =100

in a isosceles triangle opposite angles are equal so the

two angles are 40