Takes the cosine of a number (usually, an angle).

cos(*angle*)

**Menu Location**

Press the COS button to enter cos(.

This command works on all calculators.

1 byte

The `cos()` command returns the cosine of an angle measure. Naturally, the result depends on the angle mode the calculator is in: radian, degree, or (in AMS version 3.10) gradian. You can also use one of the ^{r}, `°`, ^{G} marks to specify an angle mode.

For many common angles, `cos()` can compute an exact result. Other angles, the calculator will leave alone unless it's in approximate mode (or unless you make it approximate), and then it will give a decimal approximation. As long as the calculator is in radian mode, `cos()` can be used with complex numbers as well.

```
:cos(60°)
1/2
:cos(x+2π)
cos(x)
:cos(πi/2)
cosh(π/2)
```

If `cos()` is applied to a list, it will take the cosine of every element in the list.

# Advanced Uses

The `cos()` of a matrix is not (in general) the same as taking the cosine of every element of the matrix. A different definition is used to compute the result; see Matrices and Their Commands. It requires the matrix to be square and diagonalizable in order to apply.

# Error Conditions

**230 - Dimension** happens when taking `cos()` of a matrix that isn't square.

**260 - Domain error** happens when taking `cos()` of a complex number in degree or gradian mode.

**665 - Matrix not diagonalizable** happens when taking `cos()` of a matrix that isn't diagonalizable.