= Colatitude
{title2=$\theta=\pi/2-\lambda$}
<Colatitude> is the <angle> from the positive polar axis, usually denoted $\theta$ with $0\leq\theta\leq\pi$. On a sphere it complements <latitude> $\lambda$: $\theta=\pi/2-\lambda$. Thus the north pole, equator and south pole have colatitudes zero, $\pi/2$ and $\pi$.
With <longitude> $\phi$, the standard <spherical coordinates> are $x=r\sin\theta\cos\phi$, $y=r\sin\theta\sin\phi$, $z=r\cos\theta$. The <surface element> is $r^2\sin\theta\,d\theta\,d\phi$, which shows why an <integral> over the sphere must include the sine weight. Some disciplines exchange the names of $\theta$ and $\phi$, so formulas should accompany symbol conventions.
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