Ux=0，uy=2y，vx=-2x，vy=0。 Partial derivatives of real and imaginary parts of two independent variables.

Let ux=vy uy=-vx to get the Cauchy Riemann equation of y = X.

That is to say, the derivable point set of f(z) is L={x+iy|x=y}

It can be seen that L is a straight line, so there is always a singularity of f(z) in the neighborhood of any point on it, so f(z) has no analytic point.

f '( 1+I)= UX+iuy = 0+I * 2 * 1 = 2i