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## Homework Statement

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?