## Pass Function to Another Function

You can use function handles as input arguments to other functions, which are called function functions . These functions evaluate mathematical expressions over a range of values. Typical function functions include `integral`, `quad2d`, `fzero`, and `fminbnd`.

For example, to find the integral of the natural log from 0 through 5, pass a handle to the `log` function to `integral`.

```a = 0; b = 5; q1 = integral(@log,a,b)```
```q1 = 3.0472 ```

Similarly, to find the integral of the `sin` function and the `exp` function, pass handles to those functions to `integral`.

`q2 = integral(@sin,a,b)`
```q2 = 0.7163 ```
`q3 = integral(@exp,a,b)`
```q3 = 147.4132 ```

Also, you can pass a handle to an anonymous function to function functions. An anonymous function is a one-line expression-based MATLAB® function that does not require a program file. For example, evaluate the integral of $x/\left({e}^{x}-1\right)$ on the range `[0,Inf]`:

```fun = @(x)x./(exp(x)-1); q4 = integral(fun,0,Inf)```
```q4 = 1.6449 ```

Functions that take a function as an input (called function functions) expect that the function associated with the function handle has a certain number of input variables. For example, if you call `integral` or `fzero`, the function associated with the function handle must have exactly one input variable. If you call `integral3`, the function associated with the function handle must have three input variables. For information on calling function functions with more variables, see Parameterizing Functions.