1. The problem statement, all variables and given/known data v is in polar coordinates and i want to fin u(x,y) knowing that v(r,theta)=u(rcos(theta),rsin(theta)) therefore, u(x,y)=v(sqrt(x^2+y^2), arctan(y/x)) v(r,theta) = 9+18cos(2(theta))-9sin(4(theta)) question: what is u(x,y)? 2. Relevant equations 3. The attempt at a solution u(x,y)=9+18cos(2arctan(y/x))-9sin(4arctan(y/x)) Is this correct and can i simplify this more? Thank you.