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Compute the arctangent, determining the quadrant
#include <math.h>
double atan2( double y,
double x );
float atan2f( float y,
float x );
- x, y
- The value (y/x) for which you want to find the angle.
libm
Use the -l m option to
qcc
to link against this library.
These functions compute the value of the
arctangent (specified in radians) of y/x,
using the signs of both arguments
to determine the quadrant of the return value.
A domain error occurs if both arguments are zero.
The arctangent of y/x, in the range (-π, π).
|
If an error occurs, these functions return 0, but this is also a valid
mathematical result.
If you want to check for errors, set
errno
to 0, call the function, and then check errno again.
These functions don't change errno if no errors occurred. |
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
int main( void )
{
printf( "%f\n", atan2( .5, 1. ) );
return EXIT_SUCCESS;
}
produces the output:
0.463648
ANSI,
POSIX 1003.1
Safety: | |
Cancellation point |
No |
Interrupt handler |
No |
Signal handler |
No |
Thread |
Yes |
acos(),
asin(),
atan(),
errno
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