1. The problem statement, all variables and given/known data Prove that a vertical line and a line going from a point on a parabola to the focus of the parabola form equal angles with the tangent line of the point on the parabola. 2. Relevant equations Focus = 1/4a (maybe relevant) 3. The attempt at a solution I know how to prove that the triangle from the vertical line, midpoint of Focus point to an arbitrary line and the point on the parabola is equal to a triangle that goes from focus point to point on parabola to midpoint. However, I have no clue how to show that these two angles are the same. I can find the slope of each line, obviously, but where to go from here?