What has remained the same and what has changed with this reflection? [Page No. 11]

In the reflection, the shape and size of the triangle remain the same, so the reflected triangle is congruent to the original. All side lengths and angles stay unchanged.

What changes is the position of the triangle. Each point moves to the opposite side of the y-axis, so the x-coordinates change sign while the y-coordinates remain the same.

Thus, a reflection preserves shape and size but changes the figure's position and orientation.