Defined in header <cmath> | ||
|---|---|---|
| (1) | ||
float atan2 ( float y, float x ); | ||
float atan2f( float y, float x ); | (since C++11) | |
double atan2 ( double y, double x ); | (2) | |
| (3) | ||
long double atan2 ( long double y, long double x ); | ||
long double atan2l( long double y, long double x ); | (since C++11) | |
Promoted atan2 ( Arithmetic1 y, Arithmetic2 x ); | (4) | (since C++11) |
y/x using the signs of arguments to determine the correct quadrant.double. If any argument is long double, then the return type Promoted is also long double, otherwise the return type is always double.| x, y | - | values of floating-point or integral types |
y/x (arctan(| y |
| x |
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.
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),
x and y are both zero, domain error does not occur x and y are both zero, range error does not occur either y is zero, pole error does not occur y is ±0 and x is negative or -0, ±π is returned y is ±0 and x is positive or +0, ±0 is returned y is ±∞ and x is finite, ±π/2 is returned y is ±∞ and x is -∞, ±3π/4 is returned y is ±∞ and x is +∞, ±π/4 is returned x is ±0 and y is negative, -π/2 is returned x is ±0 and y is positive, +π/2 is returned x is -∞ and y is finite and positive, +π is returned x is -∞ and y is finite and negative, -π is returned x is +∞ and y is finite and positive, +0 is returned x is +∞ and y is finite and negative, -0 is returned x is NaN or y is NaN, NaN is returned 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.
#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:
(+1,+1) cartesian is (1.41421,0.785398) polar (+1,-1) cartesian is (1.41421,2.35619) polar (-1,-1) cartesian is (1.41421,-2.35619) polar (-1,+1) cartesian is (1.41421,-0.785398) polar atan2(0, 0) = 0 atan2(0,-0) = 3.14159 atan2(7, 0) = 1.5708 atan2(7,-0) = 1.5708
|
(C++11)(C++11) | computes arc sine (arcsin(x)) (function) |
|
(C++11)(C++11) | computes arc cosine (arccos(x)) (function) |
|
(C++11)(C++11) | computes arc tangent (arctan(x)) (function) |
| returns the phase angle (function template) |
|
applies the function std::atan2 to a valarray and a value (function template) |
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