WOLFRAM|DEMONSTRATIONS PROJECT

Reflecting in Intersecting Lines

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rotate blue-green line
rotate green-red line
blue-to-green lines
red-to-green lines
circles
Reflect the blue triangle in the blue-green line to form the green image. Reflect the green triangle in the green-red line to form the red image. The red triangle, being reflected twice, is oriented like the blue triangle.
Ignoring the green triangle, the result of the two reflections is to rotate the blue triangle to the red triangle about the intersection of the two mirror lines through twice the angle between them.