Question

Write a relation between the exterior angle of a triangle with interior opposite angles

Answer 1

We have the exterior angle property of a triangle which states that an exterior angle of a triangle is equal to the sum of its interior opposite angles.

Let $ABC$ be a triangle and $\angle 1,\angle 2,\angle 3$ are interior angles and $\angle 4$ is an exterior angle as shown in the following figure

Then, by the exterior angle property

$\angle 1+\angle 2=\angle 4....\left(i\right)$

Hence, the equation $\left(i\right)$ is the relation between the exterior angle of a triangle with interior opposite angles