Surface integrals prolbem? if the mass per unit area of a surface is given by ρ=xy, find the mass if s is the part of the cylinder x^2+z^2=25 which is in the first octant and contained within the cylinder x^2+y^2=16.
so here was my attempt.
i parametrized the curve.
x^2+z^2=25
r(u, v) = < 5cos(u), v, 5sin(u)>
i then plugged into