What happens when you compose two reflections? Move the point P to see what happens when it is reflected over line n (to point P') and then over line m (to point P''). Change line n by moving point Q. What is the combined effect of the two reflections?
Composing two reflections yields a rotation (a rotation of twice the angle between the two lines, about their point of intersection). So, what happens when you compose two rotations? The app below shows the results of rotating the Hokie bird through angle A and then angle B. It also shows what happens to the Hokie bird when reflected over the two lines that make up each rotation. Try moving the original Hokie bird (the one with blue dots) and see the effects of each reflection and rotation, as well as their compositions.