Parabola, focus, directrix and area of parabolic segment

Parabolic segment psABP is 4/3 area of polygon a=ABP. F - focus, p - parabola, d - directrix, b=ABF, c=ABCD, h - perpendicular of d, E - center of AB. psABP+b=(c-psABP)/2. https://en.wikipedia.org/wiki/The_Quadrature_of_the_Parabola
– Dmitry Ezhov

Information: Parabola, focus, directrix and area of parabolic segment