Soundwaves - Calculate phase from distance

[zaza]

Don't tell me you've forgotten the cosine rule.

a² = b² + c² - 2bc cos A

where the angle A is opposite the side a. THe length you want (r2) is opposite the only angle you know (a0).

The side a depends on knowing the lengths of the other two sides and the angle A opposite the side you want to find.

If a = r2, b = d/2, c = r0 and A = a0, then you just fill in the numbers.

The same goes for the other one, but A = 180 - a0