plot_real_imag(sqrt(x), (x, -3, 3))
# Expected:
## Plot object containing:
## [0]: cartesian line: (re(x)**2 + im(x)**2)**(1/4)*cos(atan2(im(x), re(x))/2) for x over (-3.0, 3.0)
## [1]: cartesian line: (re(x)**2 + im(x)**2)**(1/4)*sin(atan2(im(x), re(x))/2) for x over (-3.0, 3.0)