Surjection/Examples/Real Sine Function to Image

Example of Surjection
Let $I$ denote the closed real interval $\closedint {-1} 1$.

Let $f: \R \to I$ be the mapping defined on the set of real numbers as:
 * $\forall x \in \R: \map f x = \sin x$

where $\sin$ denotes the sine function.

Then $f$ is a surjection, but not an injection.