A(n) angle of a triangle is equal to the sum of the two remote interior angles. exterior interior complementary vertical

∠A, ∠B, ∠C - interior angles of a triangle.
∠A 1 , ∠B 1 , ∠C 1 - exterior angles of a triangle.
∠A + ∠B + ∠C = 180°
∠A + ∠A 1 = 180°
Therefore: ∠A 1 = ∠B + ∠C ( two remote interior angles )

An exterior angle of a triangle is equal to the sum of the two remote interior angles.

An exterior angle of a triangle is equal to the sum of the two remote interior angles.