# Math Help - Domain

1. ## Domain

find the domain of -4sin(3x)

2. sin(x) is defined for all real numbers, so are sin(3x) and -4sin(3x)

3. Originally Posted by papex
sin(x) is defined for all real numbers, so are sin(3x) and -4sinsin(3x)
I want to find the domain of -4 sin (3x).

4. Hello winsome

Do you understand what is meant by the word domain of a function? It is the set of valid inputs to that function. For example, the domain of $\sqrt x$ is the set of non-negative numbers.

Now, as papex has said, $\sin x$, and therefore $\sin3x$ and $-4\sin 3x$, are defined for all values of $x$. In other words, the domain of these functions is the set of all real numbers.

There are various ways of writing this set. One is to use the symbol $\mathbb{R}$. Another is to use interval notation: $(-\infty, +\infty)$.