# Thread: Help with spherical coordinate question on Phi

1. ## Help with spherical coordinate question on Phi

not sure about the last question ;/

How come it isn't 0 to pi?

2. ## Re: Help with spherical coordinate question on Phi

Originally Posted by lc99

not sure about the last question ;/

How come it isn't 0 to pi?
In spherical coordinates $\displaystyle \phi$ goes from $\displaystyle 0 \text{ to } 2 \pi$ about the z axis. Since the graph of the cone is around the whole z axis then $\displaystyle \phi$ has the given domain.

-Dan

3. ## Re: Help with spherical coordinate question on Phi

I've tried [0,2pi] as an answer but it's incorrect.

4. ## Re: Help with spherical coordinate question on Phi

Originally Posted by lc99
I've tried [0,2pi] as an answer but it's incorrect.
Did you try $[0,2\pi)$?

5. ## Re: Help with spherical coordinate question on Phi

Still not correct unfortunately. And ran out of tries. I typed [0,2pi) with the pi symbol exactly. It seems right. Perhaps the notation?

6. ## Re: Help with spherical coordinate question on Phi

I think you are all looking at the wrong angle. $\phi$ measures the angle from the $z$ axis to the surface. It is $\theta$ that goes from $0$ to $2\pi$ (the usual polar coordinate angle). You can tell that from the equation $r = g(\theta,z)$. For $\phi$ you have to go between the asymptotes. I would try $\phi \in (\frac \pi 4,\frac {3\pi} 4)$.