If cos x=8/17, and 3π2<x<2π, what is sin(x−π)?

Question

Answer 1

1) sin(x-pi)=sinxcos(pi)-cosxsin(pi) ... sin(pi)=0, cos(pi)=-1 thus sin(x-pi)=-sinx

2) cos(x) = 8/17 ... sin(x) = sqrt(1-(8/17)^2)= 15/17

3) -sinx = -15/17