Two Reflections

Author:
Roy Wright
A triangle is shown in solid black. The red triangle is its reflection across the red line. The blue triangle is the reflection of the first reflection across the blue line. The red and blue lines can be moved around. By reflecting a figure (such as the black triangle here) across two lines, one after the other, you can slide the figure into just about any position you'd like. See if you can set up the two lines of reflection just right so that the blue triangle lines up with one of the target triangles, shown with dashed sides (------). Can you describe a general strategy to pull this off?