Consider the cylindrical can of radius 1 with a

differentiable board in the counter-clockwise's direction. Calculate:

:

OBS.: there is the figure of the cylinder and the curve, but it just says that the curve is closed and impossible to be parametrized.

A.: 3pi

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Attempt:

Parametrization: S --> (cosv, senv, u)

n = (-cosv, sinv, 0)

Where is the mistake?