Question

question
a figure containing ∠def is dilated by a scale factor of $\frac{1}{3}$ to form a new figure which contains ∠def. ∠def measures 40°. what is the measure of ∠def?

Explanation:

Step1: Recall dilation property

Dilation preserves angle - measures.
So, $\angle DEF=\angle D'E'F'$.

Step2: Substitute given value

Since $\angle D'E'F' = 40^{\circ}$, then $\angle DEF=40^{\circ}$.

Answer:

$40^{\circ}$