Rotation is one of the three rigid transformation of which others are reflection and translation. In a rotation transformation of a figure about a fixed point, known as the center of rotation, the figure is turned in a circular path about the fixed point or center of rotation. The size and shape of the pre-image the rotation are the same however, depending on the angle of rotation, their facing directions may be different. The specification of a rotation can be in the clockwise direction or in the anti-clockwise direction
The shape of the triangle in the question and the image are the same and are therefore congruent. All interior angles of the triangle and those of its rotation will therefore be congruent.
