- Alla Stolyarevska
Proposition 14. The tangent to the parabola at the point M(x,y) is the bisector of the angle adjacent to the angle between the segment, which connects M(x,y) with focus, and the ray emerging from this point in the direction of the axis of the parabola.
Supplementary problems: 1) Try to measure the angles and draw the conclusion. 2) Two tangents drawn to the parabola from a point located on the directrix. Prove that they are mutually perpendicular, and the segment connecting the point of contact passes through the focus.