# Spherical coordinates confusion

I am accustomed to
##x=rcos(\theta)sin(\phi)##
##y=rsin(\theta)sin(\phi)##
##z=rcos(\phi)##
##-\pi<\theta<\pi##, ##-\pi/2 < \phi < \pi/2##

but see some people using these instead
##x=rcos(\theta)cos(\phi)##
##y=rsin(\theta)cos(\phi)##
##z=rsin(\phi)##
##-\pi<\theta<\pi##, ##-\pi/2 < \phi < \pi/2##

Have you seen this before?
The second set seems to be "oblate spheroidal coordinates" (http://en.wikipedia.org/wiki/Oblate_spheroidal_coordinates) in the limit where the oblate spheroid is actually a sphere (the argument of the hyperbolic sin/cos is large enough so that
##asinh(\mu)=acosh(\mu)=r=\mbox{const}##

Does this make sense?

## Answers and Replies

Thanks jedishrfu, I just checked one article that uses these and indeed, the ##\phi## angle is relative to the XY-pane! Also, some use
x=rcos(θ)cos(ϕ)
y=rsin(θ)cos(ϕ)
z=-rsin(ϕ)
−π<θ<π, −π/2<ϕ<π/2
which probably work fine, even though the "minus" sign in z doesn't match the definition of "oblate spheroidal coordinates" (because the hyperbolic functions are assumed positive there)

If
z=-rsin(ϕ)

doesn't seem right, please post.

HallsofIvy
I have always seen $\rho$ rather than r but using $\phi$ to mean the angle a line from the origin to the point makes with the z-axis is a "mathematics" notation while using $\theta$ for that is a "physics" notation.