In this video, starting with a point (focus) and a line below the point (directrix), Sal tries to find the set of all points (locus) central to the point and the line. Using the distance formula, he shows that we have a parabola equation.

Starting with a point (focus) and a line below the point (directrix), in this video, Sal tries to find the set of all points (locus) equidistant to the point and the line. He shows, using the distance formula, that indeed, we have an...