The GNU C Library - Trig Functions

Trigonometric Functions

These are the familiar sin , cos , and tan functions. The arguments to all of these functions are in units of radians; recall that pi radians equals 180 degrees.

The math library doesn't define a symbolic constant for pi, but you can define your own if you need one:

	#define PI 3.14159265358979323846264338327

You can also compute the value of pi with the expression acos (-1.0) .

Function double sin (double x)

This function returns the sine of x, where x is given in radians. The return value is in the range -1 to 1 .

Function double cos (double x)

This function returns the cosine of x, where x is given in radians. The return value is in the range -1 to 1 .

Function double tan (double x)

This function returns the tangent of x, where x is given in radians.

The following errno error conditions are defined for this function:

ERANGE

Mathematically, the tangent function has singularities at odd multiples of pi/2. If the argument x is too close to one of these singularities, tan sets errno to ERANGE and returns either positive or negative HUGE_VAL .