Question

estimate the measure of this angle within 10°.

Explanation:

Step1: Recall angle - size reference

A right - angle is $90^{\circ}$.

Step2: Compare the given angle

The given angle is less than a right - angle. It looks to be about half of a right - angle. Since half of $90^{\circ}$ is $45^{\circ}$, and we need an estimate within $10^{\circ}$, a reasonable estimate is $40^{\circ}$.

Answer:

$40^{\circ}$