A spherical cap of radius p and height h is cut from a sphere of radius r. Show that the volume of the spherical cap can be expressed as:

a) V = (1/3)πh^2(3r - h)

b) V = (1/6)πh(3p^2 + h^2)

i tried setting up a coordinate system with the origin at the center of the sphere. so i am taking he integral fro (r - h) to r. i used similar triangles and established the fact that a = p(h-y) / h where a is the radius at any point along the y axis of the spherical cap and y is the height at any point along the y axis of the spherical cap. Then i found the area of a cross section by πa^2 = πp^2(h-y)^2 / h^2 and integrated that with respect to y from (r-h) to r. i treated πp^2/h^2 as a constant and found the integral of (h-y)^2. i ended up with something like π(p^2)(h)/3 - πp^2 + π(p^2)(r^2)/h. i am not sure how to get my answer to look like a or b. is my method correct or did i do something wrong?