std:: atan, std:: atanf, std:: atanl
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Defined in header
<cmath>
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| (1) | ||
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float
atan
(
float
num
)
;
double
atan
(
double
num
)
;
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(until C++23) | |
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/* floating-point-type */
atan ( /* floating-point-type */ num ) ; |
(since C++23)
(constexpr since C++26) |
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float
atanf
(
float
num
)
;
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(2) |
(since C++11)
(constexpr since C++26) |
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long
double
atanl
(
long
double
num
)
;
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(3) |
(since C++11)
(constexpr since C++26) |
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Additional overloads
(since C++11)
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Defined in header
<cmath>
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||
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template
<
class
Integer
>
double atan ( Integer num ) ; |
(A) | (constexpr since C++26) |
std::atan
for all cv-unqualified floating-point types as the type of the parameter.
(since C++23)
|
A)
Additional overloads are provided for all integer types, which are treated as
double
.
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(since C++11) |
Parameters
| num | - | floating-point or integer value |
Return value
If no errors occur, the arc tangent of num ( arctan(num) ) in the range [-| π |
| 2 |
| π |
| 2 |
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 .
If the implementation supports IEEE floating-point arithmetic (IEC 60559),
- If the argument is ±0, it is returned unmodified.
- If the argument is +∞, +π/2 is returned.
- If the argument is -∞, -π/2 is returned.
- If the argument is NaN, NaN is returned.
Notes
POSIX specifies that in case of underflow, num is returned unmodified, and if that is not supported, an implementation-defined value no greater than DBL_MIN , FLT_MIN , and LDBL_MIN is returned.
The additional overloads are not required to be provided exactly as (A) . They only need to be sufficient to ensure that for their argument num of integer type, std :: atan ( num ) has the same effect as std :: atan ( static_cast < double > ( num ) ) .
Example
#include <cmath> #include <iostream> int main() { std::cout << "atan(1) = " << std::atan(1) << '\n' << "4*atan(1) = " << 4 * std::atan(1) << '\n'; // special values std::cout << "atan(Inf) = " << std::atan(INFINITY) << '\n' << "2*atan(Inf) = " << 2 * std::atan(INFINITY) << '\n' << "atan(-0.0) = " << std::atan(-0.0) << '\n' << "atan(+0.0) = " << std::atan(0) << '\n'; }
Output:
atan(1) = 0.785398 4*atan(1) = 3.14159 atan(Inf) = 1.5708 2*atan(Inf) = 3.14159 atan(-0.0) = -0 atan(+0.0) = 0
See also
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(C++11)
(C++11)
|
computes arc sine (
arcsin(x)
)
(function) |
|
(C++11)
(C++11)
|
computes arc cosine (
arccos(x)
)
(function) |
|
(C++11)
(C++11)
|
arc tangent, using signs to determine quadrants
(function) |
|
(C++11)
(C++11)
|
computes tangent (
tan(x)
)
(function) |
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(C++11)
|
computes arc tangent of a complex number (
arctan(z)
)
(function template) |
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applies the function
std::atan
to each element of valarray
(function template) |
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C documentation
for
atan
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