std::atan2,std::atan2f,std::atan2l (3) Linux Manual Page
std::atan2,std::atan2f,std::atan2l – std::atan2,std::atan2f,std::atan2l
Synopsis
Defined in header <cmath>
float atan2 ( float y, float x );
float atan2f( float y, float x ); (since C++11)
double atan2 ( double y, double x ); (1) (2)
long double atan2 ( long double y, long double x );
long double atan2l( long double y, long double x ); (3) (since C++11)
Promoted atan2 ( Arithmetic1 y, Arithmetic2 x ); (4) (since C++11)
1-3) Computes the arc tangent of y/x using the signs of arguments to determine the correct quadrant.
4) A set of overloads or a function template for all combinations of arguments of arithmetic type not covered by 1-3). If any argument has integral_type, it is cast to double. If any argument is long double, then the return type Promoted is also long double, otherwise the return type is always double.
Parameters
x, y – values of floating-point or integral_types
Return value
If no errors occur, the arc tangent of y/x (arctan(
y
x
)) in the range [-π , +π] radians, is returned.
Y argument
Return value
X argument
If a domain error occurs, an implementation-defined value is returned (NaN where supported)
If a range error occurs due to underflow, the correct result (after rounding) is returned.
Error handling
Errors are reported as specified in math_errhandling.
Domain error may occur if x and y are both zero.
If the implementation supports IEEE floating-point arithmetic (IEC 60559),
* If x and y are both zero, domain error does not occur
* If x and y are both zero, range error does not occur either
* If y is zero, pole error does not occur
* If y is ±0 and x is negative or -0, ±π is returned
* If y is ±0 and x is positive or +0, ±0 is returned
* If y is ±∞ and x is finite, ±π/2 is returned
* If y is ±∞ and x is -∞, ±3π/4 is returned
* If y is ±∞ and x is +∞, ±π/4 is returned
* If x is ±0 and y is negative, -π/2 is returned
* If x is ±0 and y is positive, +π/2 is returned
* If x is -∞ and y is finite and positive, +π is returned
* If x is -∞ and y is finite and negative, -π is returned
* If x is +∞ and y is finite and positive, +0 is returned
* If x is +∞ and y is finite and negative, -0 is returned
* If either x is NaN or y is NaN, NaN is returned
Notes
std::atan2(y, x) is equivalent to std::arg(std::complex<double>(x,y))
POSIX_specifies that in case of underflow, y/x is the value returned, and if that is not supported, and implementation-defined value no greater than DBL_MIN, FLT_MIN, and LDBL_MIN is returned.
Example
// Run this code
#include <iostream>
#include <cmath>
int main()
{
// normal usage: the signs of the two arguments determine the quadrant
std::cout << "(+1,+1) cartesian is (" << hypot(1, 1)
<< ',' << atan2(1, 1) << ") polar\n" // atan2(1,1) = +pi/4, Quad I
<< "(+1,-1) cartesian is (" << hypot(1, -1)
<< ',' << atan2(1, -1) << ") polar\n" // atan2(1, -1) = +3pi/4, Quad II
<< "(-1,-1) cartesian is (" << hypot(-1, -1)
<< ',' << atan2(-1, -1) << ") polar\n" // atan2(-1,-1) = -3pi/4, Quad III
<< "(-1,+1) cartesian is (" << hypot(-1, 1)
<< ',' << atan2(-1, 1) << ") polar\n"; // atan2(-1,-1) = -pi/4, Quad IV
// special values
std::cout << "atan2(0, 0) = " << atan2(0, 0)
<< " atan2(0,-0) = " << atan2(0, -0.0) << '\n'
<< "atan2(7, 0) = " << atan2(7, 0)
<< " atan2(7,-0) = " << atan2(7, -0.0) << '\n';
}
Output:
See also
asin
asinf
asinl computes arc sine (arcsin(x))
(C++11)
(C++11)
acos
acosf
acosl computes arc cosine (arccos(x))
(C++11)
(C++11)
atan
atanf
atanl computes arc tangent (arctan(x))
(C++11)
(C++11)
arg (function template)
atan2(std::valarray) (function template)