# Spherical cylindrical and rectangular coordinates

1. Oct 21, 2013

### Justabeginner

1. The problem statement, all variables and given/known data
Suppose that in spherical coordinates the surface S is given by the equation rho * sin(phi)= 2 * cos(theta).
Find an equation for the surface in cylindrical and rectangular coordinates. Describe the surface- what kind of surface is S?

2. Relevant equations

3. The attempt at a solution
r= rho * sin (phi)
r^2= (rho * sin(phi)^2
r^2= 4 cos ^2 (theta)
x^2 + y^2= 4 cos^2 (theta)

And now I'm drawing a blank. Can someone please help me on how to continue?- I'm clueless! Thank you!

2. Oct 21, 2013

### LCKurtz

You don't want to square that first equation $r =\rho\sin\phi$. So after that first step you have $r = 2\cos\theta$. What's the formula for $\cos\theta$? Get it all in terms of $x,y,z$.