Question

Exterior angle and its adjacent interior angle form a ____________.

Answer 1

Firstly let a triangle, $△PQR$.

From the above $△PQR$, the angles $\angle PQR,\angle QPR,$ and $\angle PRQ$ are interior angles, and $\angle PRS$ is an adjacent angle of

$\angle PRQ$.

So, $\angle PRQ$ $+$ $\angle PRS$ $={180}^o$$=straightangle.$

Hence, the Exterior angle and its adjacent interior angle form a Straight angle.