The function is 6sin2(9x)

This question requires me to change the orginal function to taylor series. I know sinx is [(-1)^n/(2n+1)!] x^(2n+1) and cos x is [(-1)^n/(2n)!] x^(2n), but I have no idea how to simplify this by using trig identity to get the answer I want.

I need to change the function to this form below.

n=1infinity=