Solution
= Solution
Using the physics convention for <spherical coordinates>, the <polar angle> $\theta$ is measured from positive $z$ and the <azimuth> $\phi$ from positive $x$ toward positive $y$. The <Cartesian coordinates> are
$$
\boxed{x=r\sin\theta\cos\phi,\qquad y=r\sin\theta\sin\phi,\qquad z=r\cos\theta}.
$$