For a nonzero complex number $a+ib$, the argument is the directed angle from the positive real axis to the vector $(a,b)$; depending on the signs of a and b, it is $0$, $\pi$, $\frac{\pi }{2}$, $-\frac{\pi }{2}$, $\mathrm{atan}\left(\frac{b}{a}\right)$, $\mathrm{atan}\left(\frac{b}{a}\right)+\pi$ or $\mathrm{atan}\left(\frac{b}{a}\right)-\pi$:

ⅰ $\arg (3+4i)$ = $\arctan \left(\frac{4}{3}\right)$

▶Result:   $\arctan \left(\frac{4}{3}\right)$

The numeric value of: $\arctan \left(\frac{4}{3}\right)$ is:

▷ $\approx 0.9273$