Solución
∬
S
(
r
o
t
F
⋅
N
)
d
S
=
π
a
2
\iint_S (rot\; \bold{F}\cdot\bold{N})dS = \pi a^2
∬
S
(
ro
t
F
⋅
N
)
d
S
=
π
a
2