## XPath/XQuery cos function

### Summary

Returns the cosine of the argument. The argument is an angle in radians.

### Signature

`math:cos`(
`\$θ` as `xs:double?`
) as `xs:double?`

### Properties

This function is deterministic, context-independent, and focus-independent.

### Rules

If `\$` θ is the empty sequence, the function returns the empty sequence.

If `\$` θ is positive or negative infinity, or `NaN`, then the result is `NaN`.

Otherwise the result is the cosine of `\$` θ (which is treated as an angle in radians) as defined in the specification of the `cos` function applied to 64-bit binary floating point values.

### Examples

The expression `math:cos(())` returns `()`.

The expression `math:cos(0)` returns `1.0e0`.

The expression `math:cos(-0.0e0)` returns `1.0e0`.

The expression `math:cos(math:pi() div 2)` returns `0.0e0`.

The expression `math:cos(-math:pi() div 2)` returns `0.0e0`.

The expression `math:cos(math:pi())` returns `-1.0e0`.

The expression `math:cos(xs:double('NaN'))` returns `xs:double('NaN')`.

The expression `math:cos(xs:double('INF'))` returns `xs:double('NaN')`.

The expression `math:cos(xs:double('-INF'))` returns `xs:double('NaN')`.

### Notes

The treatment of the `invalidOperation` exception is defined in .

If `\$` θ is positive or negative zero, the result is `\$` θ.

If `\$` θ is positive or negative infinity, or `NaN`, then the result is `NaN`.

Otherwise the result is always in the range -1.0e0 to +1.0e0