If w = u(x, y) + iv(x, y) is an analytic function of z = x + iy, then \(\rm \frac{dw}{dz}\) equals
1
\(\rm i\frac{ \partial w}{ \partial x}\)
2
\(\rm - i\frac{ \partial w}{ \partial x}\)
3
\(\rm i\frac{ \partial w}{ \partial y}\)
4
\(\rm -i\frac{ \partial w}{ \partial y}\)