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{{ printedBook.courseTrack.name }} {{ printedBook.name }} To find the measure of the angle of rotation of $ABCD$ about the origin, it is enough to compare one of the vertices of $ABCD$ and its corresponding image.

Let's compare $A$ and $A_{′}.$ Knowing that the center of rotation is the *origin,* we will first draw two segments from $A$ and $A_{′}$ to the origin. Then, we will determine the angle between the segments.

As we can see above, the segments form a straight angle. Therefore, the measure of the angle of rotation is $180_{∘}.$