An exterior angle of a triangle is 80 degrees, one of its opposite interior angles is 60 degrees Then - Maths - Congruence of Triangles

Question

An exterior angle of a triangle is 80 degrees, one of its opposite
interior angles is 60 degrees Then the measure of other interior
opposite angle is

Varun.Rawat · Accepted Answer

Let ABC be the ∆ in which side BC is produced to D such that ∠ACD is the exterior angle
Let ∠ACD = 80°Now, ∠ABC and ∠BAC are the interior  opposite angles
Let ∠ABC = 60°Now, ∠BAC = ?We know that, ,easure of exterior angle is equal to sum of interior opposite angles
Now, ∠ACD = ∠ABC + ∠BAC⇒80° = 60° + ∠BAC⇒∠BAC = 20°

An exterior angle of a triangle is 80 degrees, one of its opposite interior angles is 60 degrees. Then the measure of other interior opposite angle is