1. The problem statement, all variables and given/known data Determine where r(t) is a smooth curve for -pi <t<pi R(t)= (x(t),y(t))=(4sin^3(t), 4cos^3(t)) 2. Relevant equations 3. The attempt at a solution To be honest I have no idea where to start. I know what a smooth function is but my understanding is that the sin(t) and cos(t) functions over all of t are smooth. No corners. Any starting help would be appreciated.