Answer :- An exterior angle is created by extending one side of a triangle.
Explanation:-
Let ABC a triangle with interior angles ∠A, ∠B and ∠C and one of its side AB is extended to a point P such that a new angle ∠ACP is formed outside the triangle ABC named as exterior angle of ABC.
⇒∠BCA and ∠ACP are supplementary angles.
Also the measure of exterior angle is equal to sum of the opposite interior angles of a triangle.
