Cylinder = line-segment × disc
C = | × ●
The “product rule” from calculus works as well with the boundary operator ∂ as with the differentiation operator ∂.
∂C = ∂| × ● + | × ∂●
>Oops. Typo. Sorry, I did this really late at night! cos and sin need to be swapped back.
Oops. Another typo. Wrong formula for circumference.
