cos function

Synopsis

$cos(number)

Technical

Returns the cosine of number, interpreted as an angle in radians. Finite real inputs have results between -1 and 1. The corresponding inverse operation is acos(), which returns a principal angle.

The normal rules about number arguments apply. The first argument word is converted with atof(), accepting decimal fractions and scientific notation; additional words are ignored. Missing input returns an empty string. Nonnumeric input converts to zero, and a numeric prefix can be accepted even when followed by nonnumeric text.

Returns and restrictions

The calculation uses the C library's cos() and a C double. Results are formatted with %.50g, not limited to six decimal places. The floating_point_math and floating_point_precision settings do not change the calculation or formatting. Extra displayed digits do not imply 50 digits of accuracy.

Infinite input causes a library domain error. EPIC returns DOM if the library reports it through errno; platforms that report it only through floating-point exception flags can instead return a NaN string. NaN input ordinarily produces a NaN result. The shared wrapper returns RANGE for a reported range error and an empty string for another reported error. It checks errno, not floating-point exception flags, and clears errno after argument conversion and before calculating the cosine.

Examples

The approximate examples describe numeric values; the returned strings may contain more digits.

Source

source/functions.c registers cos and implements it through the shared math-function and error-return macros. include/functions.h defines argument conversion and formatting. The C/POSIX cosine specification defines radians, special inputs, and library error reporting.