I have show that the function $\sin(z)$ satisfies the Cauchy-Riemann equations but don't know where to go from here.
If it saves some working for you they are
$$du/dx=-\sin(x)\cosh(y)$$ $$dv/dy=-\sin(x)\cosh(y)$$
$$du/dy=\cos(x)\sinh(y)$$ $$dv/dx=-\cos(x)\sinh(y)$$