TRIG(3M) — MATHEMATICAL LIBRARY

NAME

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

SYNOPSIS

#include <math.h>

double sin(double x);

double cos(double x);

double tan(double x);

double asin(double x);

double acos(double x);

double atan(double x);

double atan2(double y, double x);

DESCRIPTION

sin(x), cos(x) and tan(x) return trigonometric functions of radian arguments. Trigonometric argument reduction is carried out with respect to the infinitely precise π.

asin(x) returns the arc sine of x in the range −π/2 to π/2.

acos(x) returns the arc cosine of x in the range 0 to π.

atan(x) returns the arc tangent of x in the range −π/2 to π/2.

atan2(y,x) and hypot(x,y) (see hypot(3M)) convert rectangular coordinates (x,y) to polar (r,θ); atan2(y,x) computes θ, the argument or phase, by computing an arc tangent of y/x in the range −π to π.

RETURN VALUES

For exceptional cases, matherr(3M) tabulates the values to be returned as dictated by various Standards.

DIAGNOSTICS

In IEEE754 mode (i.e. the −xlibmieee acc compilation option), these functions handle exceptional arguments in the spirit of ANSI/IEEE Std 754-1985. sin(±∞), cos(±∞) and tan(±∞) return NaN; asin(x) and acos(x) return NaN if |x|>1. atan(±∞) returns ±π/2. For atan2(),
• atan2(±0,x) returns ±0 for x > 0 or x = +0;
• atan2(±0,x) returns ±π for x < 0 or x = −0;
• atan2(y,±0) returns π/2 for y > 0;
• atan2(y,±0) returns −π/2 for y < 0;
• atan2(±y,∞) returns ±0 for finite y > 0;
• atan2(±∞,x) returns ±π/2 for finite x;
• atan2(±y,−∞) returns ±π for finite y > 0;
• atan2(±∞,∞) returns ±π/4;
• atan2(±∞,−∞) returns ±3π/4.

Sun Release 4.1 — Last change: 22 Jul 1994

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