Exterior Angle Property
Explanation:
Interior Angle :
The angle formed with in the closed boundary of the triangle is called an interior angle.
In the given figure, α , β and γ are interior angles.
Exterior Angles:
The angle formed outside the closed boundary of the triangle is called an exterior angle.
In the given figure, γ' is an exterior angles.
Sum of the measures of the two non-adjacent interior angles is EQUAL to measure of an exterior angle of a triangle.
⇒ α + β = γ'
This property is known as " Exterior Angle Property"
Also, here angles γ and γ' are making a linear pair.
γ + γ' = 180°