To get a better look at the graph, you can click on it.

The curve above is the graph of a sinusoidal function. It goes through the points $(-9,-4)$ and $(1,-4)$. Find a sinusoidal function that matches the given graph. If needed, you can enter $\pi$=3.1416... as 'pi' in your answer, otherwise use at least 3 decimal digits.

$f(x) =$