Calculate angle of triangle Python

It's a little more compicated than that. You need to use the law of cosines

>>> A = 7
>>> B = 7
>>> C = 9.899
>>> from math import acos, degrees
>>> degrees(acos((A * A + B * B - C * C)/(2.0 * A * B)))
89.99594878743945

This is accurate to 4 significant figures. If you provide a more precise value of C, you get a more accurate result.

>>> C=9.899494936611665
>>> degrees(acos((A * A + B * B - C * C)/(2.0 * A * B)))
90.0