If $z_1$ and $z_2$ are two non-zero complex numbers such that…
If $z_1$ and $z_2$ are two non-zero complex numbers such that $\left|z_1+z_2\right|=\left|z_1\right|+\left|z_2\right|$ then $\arg z_1-\arg z_2$ is equal to
$\frac{\pi}{2}$
$-\pi$
0
$-\frac{\pi}{2}$
Solution
$\left|z_1+z_2\right|=\left|z_1\right|+\left|z_2\right| \Rightarrow z_1$ and $z_2$ are collinear and are to the same side of origin; hence $\arg z_1-\arg z_2=0$.