tan**2x - 1 = 0
Factoring the difference of two squares:
(tanx + 1) * (tanx - 1) = 0
so either tanx = -1 or tan x = 1, which occurs when |sin x| = |cos x|
this occurs at 45, 135, 225, 315, etc or 45 + 90 * n degrees, where n = 0, 1, 2, 3, ...
or pi/4, 3*pi/4, 5*pi/4, 7*pi/4 or pi/4 + pi/2 * n, where n = 0, 1, 2,3, ...