# What type of coordinate system?

1. Aug 2, 2015

### shanepitts

This is a very basic question, but what type of coordinate system is this?

When is it useful to use?

er, eθ, eΦ sinθ

2. Aug 2, 2015

### blue_leaf77

Those notations are typically used for the so-called (curvilinear) spherical coordinate system. It's useful when the system to be described has a pronounced spherical symmetry, for example our earth's magnetic field, electric field due to a charges sphere, and hydrogen atom. By the way what is that $\sin\theta$ for?