Give a parametric representation of the following surfaces in terms of the given parameter variables: a) The first octant portion of the sphere (x^2) + (y^2) + (z^2) = 16 in terms of the spherical variables theta and phi. b)The graph of the function z = (x^3) - sqrt(y) in terms of the Cartesian variables x and y. I'm not sure how to do these at all. a) It's a sphere and theta ranges from 0 to pi/2. phi ranges from 0 to pi/2. Are the parametric equations just theta = t and phi = t, given that t ranges from 0 to pi/2? Or do we substitute x = psin(phi)cos(theta), etc. I'm really not sure what to do. Help.