The theorem may be described as follows:
*Assume a parabola with two points A and B and their tangents AS and BS are given.
*Pick a number, n and divide AS and BS into n equal intervals.
*Label division points on AS with numbers 1, 2, 3, … counting from S, and mark those on BS counting from B.
*Connect the points with the same labels. From Apollonius’ theorem, the lines will envelope the parabola.