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Falkqwer
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The idea is to subtract 2pi r^2 from both sides, then divide both sides by 2r*pi to isolate h \[\Large T = 2r\pi h + 2\pi r^2\] \[\Large T - 2\pi r^2 = 2r\pi h \] \[\Large 2r\pi h = T - 2\pi r^2 \] \[\Large h = \frac{T - 2\pi r^2}{2r\pi} \]