Summing sines of different frequencies Is there a general formula for solving the following equation:
$$A \sin(Bt+C) + D \sin(Et+F) = G \sin(Ht+I)$$
All constants on the left side of the equation are known (t is a variable). Is there a formula for calculating G, H and I? Is this even solvable in general? 
I searched the web and found some semi-relevant hits, like here, but it didn't really seem to answer my question. 

And, of course,
if $B/E$ is irrational,
the resulting curve
is not even periodic.
