Find an equation of the tangent plane to the parametric surface x = 3r cos, y = 4rsin, z = r at the point 3 2,4 2,2 when r = 2, = /4. z = Note: A normal vector to a surface defined parametrically by x(r,), y(r,),z(r,) is given by the cross product < x r , y r , z r > < x , y , z > .