Format
#include <math.h> double atan(double x); double atan2(double y, double x);
Language Level: ANSI
Threadsafe: Yes.
Description
The atan() and atan2() functions calculate the arctangent of x and y/x, respectively.
Return Value
The atan() function returns a value in the range -&pi./2 to &pi./2 radians. The atan2() function returns a value in the range -&pi. to &pi. radians. If both arguments of the atan2() function are zero, the function sets errno to EDOM, and returns a value of 0.
Example that uses atan()
This example calculates arctangents using the atan() and atan2() functions.
#include <math.h> #include <stdio.h> int main(void) { double a,b,c,d; c = 0.45; d = 0.23; a = atan(c); b = atan2(c,d); printf("atan( %lf ) = %lf/n", c, a); printf("atan2( %lf, %lf ) = %lf/n", c, d, b); } /**************** Output should be similar to ****************** atan( 0.450000 ) = 0.422854 atan2( 0.450000, 0.230000 ) = 1.098299 *****************************************************************/
Related Information
(C) Copyright IBM Corporation 1992, 2006. All Rights Reserved.