The rotation (x,y) →(y,-x) maps P and P'. Find the measure of the acute or right angle formed by intersecting lines so that P can be mapped to P' using two reflections.

Answer 1

I've sketched out three possible scenarios where the points (x, y) are transformed into (y, -x). Do you see anything it common between the lines?

To map this as two reflections, we could reflect across the y-axis and then again across the diagonal line y = -x