Knowing SSA of triangle find other 2 angles approximately without inverse trig functions

This is for when you know 2 sides and an angle of a triangle and you want to find the other 2 angles approximately without using inverse trig functions...
The formula is:

In addition it gets 45-45-90 and Equilateral triangles exactly right! The 180-C can of course be replaced with pi-C when working in radians... There might be a kind of 3 variable Cauchy series that this uses averages of the first two terms of, I'll have to look further...