reflecting figure over a line (Level 3) not horizontal not vertical #2 (Delta Math)

This video deals with how to reflect an image across a reflection line that's not vertical or horizontal. (disclaimer: I speak pretty slow so 1.5x playback speed might be best) You have to find the point that lies on a perpendicular line to your line of reflection and is the same distance(equidistant) to the line of reflection as your image vertices.