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