1. The problem statement, all variables and given/known data Show that the curve with parametric equation : x = sint t; y = cos t; z = sni^2 t is the curve of intersection of the surface z = x^2 and x^2 + y^2 = 1. 3. The attempt at a solution From polor equation I know that x = rcos(t) and y = rsin(t); from this we can replace x^2 + y^2 = 1. with cos(t) + sin(t) = 1 and since z = x^2, and x = rcos(t), it follows that z = r^2cos^2(t) = cos^2(t) so we have the vector equation : v = < cos(t) , sin(t), cos^2(t). But this doesn't follow the question. Whats wrong?