Question

An exterior angle of a triangle is equal to the sum of two ______ opposite angles.

• A. interior
• B. exterior
• C. vertical
• D. none of these

Answer 1

Answer: (A)

Consider the given triangle, we can easily apply exterior angle property of triangle.

For given triangle $XYZ$,

$\angle 1+\angle 2+\angle z={180}^o$

Also, $\angle 3+\angle z={180}^o$ ......... (Linear pair of angles)

$\angle 1+\angle 2+\angle z=\angle 3+\angle z$

$\Rightarrow \angle 3=\angle 1+\angle 2$ ...... (which is the Exterior angle property).

Therefore, we can say that, an exterior angle of a triangle is equal to the sum of the two interior opposite angles.

Hence, option $A$ is correct.