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A = 4πr2

A = 4*Pi*r^2

Where A is the surface area of the sphere, r is the radius of the sphere, and Pi is a constant.

Derivation:

The volume of a sphere can be described by a number of pyramids with n-gonal bases that completely cover the sphere, with their vertices at the center of the sphere. The volume of the sphere is then

V = n×(1/3)br

where n is the number of pyramids, b is the area of one of the pyramid's bases, and r is the radius of the sphere. This equation can be rearranged to read:

V = n×b(1/3)r

But what is n×b equal to? The surface area of the sphere! Thus, we can write:

V = SA×(1/3)r

where SA is surface area.

Now it's time to start solving.

(4/3)πr³ = SA(1/3)r

(4/3)πr² = (1/3)SA

SA = 4πr²

Q.E.D.

Of course, if you know the calculus, or are a smartass, or both, then you could just show that dV/dr = SA, and ∫A dr = V. But where's the fun in that?

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