The periodic function COS returns the trigonometric cosine of X.

## Examples

Find the cosine of 0.5 radians and print the result by entering:

PRINT, COS(.5)

IDL prints:

0.877583

## Syntax

*Result* = COS(*X*)

## Return Value

Returns the trigonometric cosine of X.

## Arguments

### X

The angle for which the cosine is desired, specified in radians. If *X* is double-precision floating or complex, the result is of the same type. All other types are converted to single-precision floating-point and yield floating-point results. When applied to complex numbers:

COS(*x*) = (EXP(*i**x) + 1/EXP(*i**x))/2

where *i* is defined as COMPLEX(0, 1).

If *X* is an array, the result has the same structure, with each element containing the cosine of the corresponding element of *X*.

## Keywords

### Thread Pool Keywords

This routine is written to make use of IDL’s *thread pool*, which can increase execution speed on systems with multiple CPUs. The values stored in the !CPU system variable control whether IDL uses the thread pool for a given computation. In addition, you can use the thread pool keywords TPOOL_MAX_ELTS, TPOOL_MIN_ELTS, and TPOOL_NOTHREAD to override the defaults established by !CPU for a single invocation of this routine. See Thread Pool Keywords for details.

## Version History

Original |
Introduced |