i am trying to apprixmate the surface area of a hemisphere.
i am approximating by cutting the sphere into cylinders of different radius, and using their curved surface area to approximate.
each cylinder will have a height of r.cos.theta and radius of r.sin.theta.
so the surface area should be =
integral [pi/2 to 0] (2.pi * r.sin.theta * r.cos.theta * d.theta)??
but that gives me -pi r^2 which is wrong...
anyidea where i went wrong?