Sher Mohammad
Last Activity: 10 Years ago
Let 
The normal at P intersects the parabola again at Q
slope(PQ) = m and the slope of the tangent line at Q is -1/n
x = the angle that PQ makes with the horizontal
y = the angle that the tangent at Q makes with the horizontal
x-y = the angle we are looking for
With tan (x) = m and tan(y) = -1/n, use the identity
