It is given that
ycosx=xsiny On taking logrithm both sides, we get
cosxlogy=sinylogx On differentiating both side w.r.t.
x, we get
y1(cosx)dxdy−(sinx)logy=x1siny+(logx)(cosy)dxd⇒dxdy(y1cosx−(logx)cosy)=x1siny+(sinx)logy⇒dxdy=x(cosx−ylogxcosy)y(siny+xsinxlogy)$$