Question

triangle abc is formed by triangle abc counterclockwise about the

Explanation:

Step1: Observe the orientation change

We see that the orientation of $\triangle ABC$ has changed to $\triangle A'B'C'$. The relative positions of the vertices have rotated.

Step2: Determine the center and angle of rotation

By comparing the positions of corresponding vertices, we can tell that the rotation is about the origin. And by analyzing the change in orientation, we can conclude that the angle of rotation is $180^{\circ}$ counter - clockwise.

Answer:

rotating, origin, $180^{\circ}$