Question

identifying isometric transformations
which rigid transformation would map the pre - image δabc to the image δabc?
a rotation by 90°
a reflection
a translation to the right
a translation up

Explanation:

A reflection flips a figure over a line. Rotation turns a figure around a point. Translation slides a figure. By observing the orientation of $\triangle ABC$ and $\triangle A'B'C'$, we see that they are mirror - images of each other. A $90^{\circ}$ rotation would change the orientation in a different way than what is shown. Translations (to the right or up) would just move the figure without flipping it. So, it is a reflection.

Answer:

a reflection