Question 69292
Using formula:
{{{cos(A-B)=cos(A)cos(B)-sin(A)sin(B)}}}let A=x and {{{B=3pi/2}}}
{{{cos(x-3pi/2)=cos(x)cos(3pi/2)-sin(x)sin(3pi/2)}}} Since {{{cos(3pi/2)=0}}} the first term is zero
{{{cos(x-3pi/2)=0-sin(x)sin(3pi/2)}}} Since {{{sin(3pi/2)=-1}}} the answer comes to sin(x)
{{{cos(x-3pi/2)=-sin(x)(-1)}}}
{{{cos(x-3pi/2)=sin(x)}}}