1. The problem statement, all variables and given/known data Find the curvature of r(t)=2ti+2tj+k. 2. Relevant equations None. 3. The attempt at a solution The answer is 0 in the book. I know the formula for curvature is k(t)=abs(r'(t)xr"(t))/abs(r'(t))^3. I know that r'(t)=2i+2j and r"(t)=0, so r'(t)xr"(t)=0? How to find r'(t)xr"(t) and r'(t)^3?