Question

if the vertical angle of iscoceleas triangle is 100 then find the base angle

Answer 1

the base angles will be 40 each

Answer 2

Vertical angle of the isosceles triangle = 100 degrees.

Now. the base angles  of an isosceles triangle are equal.
 let the base angle be x degrees.

So, by the angle sum property of triangle
100 + x + x = 180
2x = 80
x = 40 degrees.