Solve for x.?

Question

50cos9x = -240 + 15 (w + (sqr rt of (57 + 50sin9x)/16))
Please include steps and perhaps rationale.

Answer 1

What is w???

Anyhow, the main point is to substitute a variable y = 50sin9x.

Then cos9x = ... well, you know what it equals in terms of y.

Then with a little fiddling you get a polynomial equation in y and solve it. From there it's no problem getting x.