Answer
See below.
Work Step by Step
The volume of the sphere: $\frac{4}{3}r^3\pi$
The volume of the inscribed cone: $\pi r^2h$
These two are equal, thus $\frac{4}{3}r^3\pi=\pi r^2h\\\frac{4}{3}r=h$
Thus we proved what we had to.
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