1. The problem statement, all variables and given/known data I have got double contour integral: And here is picture: I know every line equation as well. The task is to calculate this integral as: 1. surface integral of outside of the area (in the picture) 2. using Ostrogradsky formula 2. Relevant equations Equation of plane: 4x+3y+12z-12=0 It means that x=3-0.75y-3z and z=1-0.25y-(1/3)x 3. The attempt at a solution I guess, this can be integral for task 1, when we use surface integral: Can someone chek, if it's correct? And how to start task 2, when I have to use Ostrogradsky formula?