Question

Identify the domain of this function

Answer 1

When you think of domain, you always think x-values. so the domain values for this graph is (-∞,∞).

Answer 2

This is a graph of sine. Domain is equal the set of all real numbers:

$D=\mathbb{R}=(-\infty,\ \infty)$

The domain is x-y, for which there is a graph.