1. The problem statement, all variables and given/known data For the surface with parametric equations r(st)=<st, s+t, s-t>, find the equation of the tangent plane at (2,3,1). Find the surface area under the restriction s^2 + t^2 <=(lessthanorequalto) 1 2. Relevant equations 3. The attempt at a solution I already figured out the equation of the tangent plane: -2x+3y-z=4, but I am not sure how to find the surface area? I want to use the SA equation |rs x rt| integrated from ds 0 to 1 and dt 0 to 2pi but i am not having much luck. Any ideas?