atan, atan2 (Windows CE 5.0)
Developing an Application > Microsoft C Run-time Library for Windows CE > Run-time Library Reference
Calculates the arctangent of x (atan) or the arctangent of y/x (atan2).
double atan(doublex);double atan2(doubley, doublex);
Parameters
- x, y
Any numbers.
Return Values
atan returns the arctangent of x.
atan2 returns the arctangent of y/x.
If x is 0, atan returns 0.
If both parameters of atan2 are 0, the function returns 0.
atan returns a value in the range –π/2 to π/2 radians.
atan2 returns a value in the range –π to π radians, using the signs of both parameters to determine the quadrant of the return value.
Remarks
atan calculates the arctangent of x.
atan2 calculates the arctangent of y/x.
atan2 is well defined for every point other than the origin, even if x equals 0 and y does not equal 0.
Example
/* ATAN.C: This program calculates
* the arctangent of 1 and -1.
*/
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 );
}
Output
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
Requirements
OS Versions: Windows CE 2.0 and later.
Header: stdlib.h.
Link Library: coredll.dll.
See Also
Send Feedback on this topic to the authors