NAME

trig: sin, cos, tan, asin, acos, atan, atan2 − trigonometric functions

SYNOPSIS

#include <math.h>

double sin (x)
double x;

double cos (x)
double x;

double tan (x)
double x;

double asin (x)
double x;

double acos (x)
double x;

double atan (x)
double x;

double atan2 (y, x)
double y, x;

DESCRIPTION

sin, cos and tan return respectively the sine, cosine, and tangent of their argument, x, measured in radians.

asin returns the arcsine of x, in the range [−π/2,π/2].

acos returns the arccosine of x, in the range [0,π].

atan returns the arctangent of x, in the range [−π/2,π/2].

atan2 returns the arctangent of y/x, in the range (−π,π], using the signs of both arguments to determine the quadrant of the return value.

SEE ALSO

matherr(3M)

DIAGNOSTICS

sin, cos, and tan lose accuracy when their argument is far from zero.  For arguments sufficiently large, these functions return zero when there would otherwise be a complete loss of significance.  In this case a message indicating TLOSS error is printed on the standard error output.  For less extreme arguments causing partial loss of significance, a PLOSS error is generated but no message is printed.  In both cases, errno is set to ERANGE. 

If the magnitude of the argument of asin or acos is greater than one, or if both arguments of atan2 are zero, zero is returned and errno is set to EDOM.  In addition, a message indicating DOMAIN error is printed on the standard error output. 

These error-handling procedures may be changed with the function matherr(3M).

September 02, 1992