aliases, multi-imports, and the `np.` you'll see everywhere

Cursor wrote this and sum no longer works the way it should. The bug: from math import * pulled in everything from math, including math.fsum, but more importantly the user also defined a local variable called sum, which silently shadows Python's built-in sum() function.

Replace the star import on line 1 with a targeted import that only brings in pi and sqrt. After that, sum([1, 2, 3]) works again. The script should print:

3.141592653589793
9.0
6