# Thread: what is the mistake here

1. ## Re: what is the mistake here

You are working with the sphere [tex]x^2+ y^2+ z^2= 2z[/itex], a sphere of radius 1, centered at (0, 0, 1). In spherical coordinates, $x= \rho cos(\theta)sin(\phi)$, $y= \rho sin(\theta)sin(\phi)$, $z= \rho cos(\theta)$. Since the radius of the sphere is 1, $\rho= 1$ and we have $x^2+ y^2+ z^2= 1$ and $2z= 2cos(\phi)$.

2. ## Re: what is the mistake here

Originally Posted by transgalactic
$z=\rho cos \theta$
what to do now?
Do you mean $\theta$ or $\phi$ ?

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