Question 1149958
<pre>
Use the formula {{{sin(A+B)=sin(A)cos(B)+cos(A)sin(B)}}}

on the left side:

{{{sin(x+pi/2)=cos(x)}}}

{{{sin(x)cos(pi/2)+cos(x)sin(pi/2)}}}

{{{sin(x)(0)+cos(x)(1)}}}

{{{cos(x)}}}

Edwin</pre>