[istillbelieve]

Hi, I'm having a lot of trouble with this question:If cos(x+3*y)=sin(2*x-y) then calculate (1/2)*(sin((20°)-(4*x/9)))*(cot((3*x+2*y)/3))*(csc((2*x+4*y)/9))I'm not sure what to do, I tried expanding both but I end up with a huge mess and cosines cubed and I feel like there is an easy way I'm overlooking because the question is not supposed to be hard and the answer is a number. Any suggestion will be appreciated.

[CWH68]

Hint: cos(w) = sin(90-w)