The vertical angle of an isosceles triangle is 100°. Find its base angles.
Consider an isosceles triangle ABC,
Such that:
AB = AC
Given,
Vertical ∠A is 100o
To find: Base angle
Since, is isosceles,
∠B = ∠C (Angle equal to opposite sides)
And,
∠A + ∠B + ∠C = 180o (Angles of triangle)
100o + ∠B + ∠B = 180o
∠B = 40o
∠B = ∠C = 40o