Originální popis anglicky:
atan2, atan2f, atan2l - arc tangent functions
Návod, kniha: POSIX Programmer's Manual
#include <math.h>
double atan2(double
y, double
x );
float atan2f(float
y, float
x);
long double atan2l(long double
y, long double
x);
These functions shall compute the principal value of the arc tangent of
y/
x, using the signs of both arguments to determine the
quadrant of the return value.
An application wishing to check for error situations should set
errno to
zero and call
feclearexcept(FE_ALL_EXCEPT) before calling these
functions. On return, if
errno is non-zero or
fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is
non-zero, an error has occurred.
Upon successful completion, these functions shall return the arc tangent of
y/
x in the range [-pi,pi] radians.
If
y is ±0 and
x is < 0, ±pi shall be returned.
If
y is ±0 and
x is > 0, ±0 shall be returned.
If
y is < 0 and
x is ±0, -pi/2 shall be returned.
If
y is > 0 and
x is ±0, pi/2 shall be returned.
If
x is 0, a pole error shall not occur.
If either
x or
y is NaN, a NaN shall be returned.
If the result underflows, a range error may occur and
y/
x should
be returned.
If
y is ±0 and
x is -0, ±pi shall be returned.
If
y is ±0 and
x is +0, ±0 shall be returned.
For finite values of ±
y > 0, if
x is -Inf, ±pi
shall be returned.
For finite values of ±
y > 0, if
x is +Inf, ±0
shall be returned.
For finite values of
x, if
y is ±Inf, ±pi/2 shall be
returned.
If
y is ±Inf and
x is -Inf, ±3pi/4 shall be
returned.
If
y is ±Inf and
x is +Inf, ±pi/4 shall be returned.
If both arguments are 0, a domain error shall not occur.
These functions may fail if:
- Range Error
- The result underflows.
If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then
errno shall be set to [ERANGE]. If the integer expression
(math_errhandling & MATH_ERREXCEPT) is non-zero, then the underflow
floating-point exception shall be raised.
The following sections are informative.
None.
On error, the expressions (math_errhandling & MATH_ERRNO) and
(math_errhandling & MATH_ERREXCEPT) are independent of each other, but at
least one of them must be non-zero.
None.
None.
atan() ,
feclearexcept() ,
fetestexcept() ,
isnan()
,
tan() , the Base Definitions volume of
IEEE Std 1003.1-2001, Section 4.18, Treatment of Error
Conditions for Mathematical Functions,
<math.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html
.
