Question 1197097
<pre>
{{{system(sin(y)=cos(2x),x+sin(y)=xy)}}}

Differentiate terme by term:

{{{system(cos(y)expr(dy/dx)=-2sin(2x),1+cos(y)expr(dy/dx)=x*expr(dy/dx)+y*1)}}}

{{{system(cos(y)expr(dy/dx)=-2sin(2x),cos(y)expr(dy/dx)=x*expr(dy/dx)+y-1)}}}

The left sides are equal, so we set the right sides equal

{{{-2sin(2x)=x*expr(dy/dx)+y-1}}}

Solve that for {{{dy/dx}}}.  You finish.

Edwin</pre>