I need help with this curverture problem. I am having troubling setting up the equations. For the curverture k, i calculated using the cross product of magnitude of the r'(t)xr"(t) and then divided by the magnitude r'(t) cubed. I took the reciprocal of that and my answer for Radius = 16^2/sqrt(257). I am not too sure of the numbers. I plugged in t=pi/2 before doing the cross product and before the cubing.

I am stuck on how to find the center and setting up the equation. I have 2 submissions left! Help would be appreciated.