Question

the vertical angle of an isosceles triangle is 100 degree.find its base angles.

Answer 1

Vertical Angle = 100°

As we Know that base angles are equal so let the base angles be = x

So, By using Angle Sum Property
$100 + x + x = 180 \\ 100 + 2x = 180 \\ 2x = 180 - 100 \\ x = \frac{80}{2}$
So, x = 40°

Therefore, the base angle is 40°

Answer 2

sum of all angle of triangle is 180
opposite angle of isosceles triangle is equal = 2x

a+b+c = 180
2x+100 = 180
2x = 180-100
2x= 80
X=40