This is Exercise EP$10$ (g) from Fernadez and Bernardes's book *Introdução às Funções de uma Variável Complexa* (in Portuguese)

How does one geometrically describes the set $S=\{z\in\mathbb{C}:|\operatorname{Arg}(z-i)|\lt\frac{\pi}{6}\}?$

I tried to solve this one as I did in others, but it did not work out as I wish. Let me show what I did so far.

$z=x+yi\in S \Longleftrightarrow |\operatorname{Arg}(z-i)|\lt\frac{\pi}{6}\Longleftrightarrow \frac{-\pi}{6}\lt \operatorname{Arg}(x+(y-1)i)\lt \frac{\pi}{6}.$

Unfortunately, I was not able to go further. I would appreciate any hint.