Calculate the arctangent of x (atan and _atanl) and the arctangent of y/x (atan2 and _atan2l).
#include <math.h>
double atan( double x );
double atan2( double y, double x );
long double _atanl( long double x );
long double _atan2l( long double y, long double x );
| x, y | Any number |
The atan family of functions calculates the arctangent of x, and the atan2 family of functions calculates the arctangent of y/x. The atan group returns a value in the range –p/2 to p/2 radians, and the atan2 group returns a value in the range Ôp to p radians. The atan2 functions use the signs of both arguments to determine the quadrant of the return value. The atan2 functions are well defined for every point other than the origin, even if x equals 0 and y does not equal 0.
The atan family of functions returns the arctangent result. If both arguments of atan2 or _atan2l are 0, the function sets errno to EDOM, prints a _DOMAIN error message to stderr, and returns 0.
Error handling can be modified by using the _matherr (or _matherrl) routine.
atan, atan2
Standards:ANSI, UNIX
16-Bit:DOS, QWIN, WIN, WIN DLL
32-Bit:DOS32X
_atanl, _atan2l
Standards:None
16-Bit:DOS, QWIN, WIN, WIN DLL
32-Bit:None
acos functions, asin functions, cos functions, _matherr, sin functions, tan functions
/* ATAN.C: This program calculates the arctangent of 1 and -1. */
#include <math.h>
#include <stdio.h>
#include <errno.h>
void main( void )
{
double x1, x2, y;
printf( "Enter a real number: " );
scanf( "%lf", &x1 );
y = atan( x1 );
printf( "Arctangent of %f: %f\n", x1, y );
printf( "Enter a second real number: " );
scanf( "%lf", &x2 );
y = atan2( x1, x2 );
printf( "Arctangent of %f / %f: %f\n", x1, x2, y );
}
Enter a real number: -862.42
Arctangent of -862.420000: -1.569637
Enter a second real number: 78.5149
Arctangent of -862.420000 / 78.514900: -1.480006