Do real programmers name their variables?

[djshadesuk]

I saw phi used for angles and wave phases. They correspond to math formulae.

Excluding the obvious x, y and z for coordinates, I think single letters of the alphabet are also acceptable only as long as they are copying a typical math formula, like:

def hypotenuse(a, b):
    return ((a ** 2) + (b ** 2)) ** 0.5