std:: cos, std:: cosf, std:: cosl
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Defined in header
<cmath>
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||
| (1) | ||
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float
cos
(
float
num
)
;
double
cos
(
double
num
)
;
|
(until C++23) | |
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/* floating-point-type */
cos ( /* floating-point-type */ num ) ; |
(since C++23)
(constexpr since C++26) |
|
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float
cosf
(
float
num
)
;
|
(2) |
(since C++11)
(constexpr since C++26) |
|
long
double
cosl
(
long
double
num
)
;
|
(3) |
(since C++11)
(constexpr since C++26) |
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Additional overloads
(since C++11)
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||
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Defined in header
<cmath>
|
||
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template
<
class
Integer
>
double cos ( Integer num ) ; |
(A) | (constexpr since C++26) |
std::cos
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
.
|
(since C++11) |
Parameters
| num | - | floating-point or integer value representing angle in radians |
Return value
If no errors occur, the cosine of
num
(
cos(num)
) in the range
[
-
1.0
,
+
1.0
]
, is returned.
|
The result may have little or no significance if the magnitude of num is large. |
(until C++11) |
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 .
If the implementation supports IEEE floating-point arithmetic (IEC 60559),
- if the argument is ±0, the result is 1.0 .
- if the argument is ±∞, NaN is returned and FE_INVALID is raised.
- if the argument is NaN, NaN is returned.
Notes
The case where the argument is infinite is not specified to be a domain error in C, but it is defined as a domain error in POSIX .
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 :: cos ( num ) has the same effect as std :: cos ( static_cast < double > ( num ) ) .
Example
#include <cerrno> #include <cfenv> #include <cmath> #include <iomanip> #include <iostream> #include <numbers> // #pragma STDC FENV_ACCESS ON constexpr double pi = std::numbers::pi; // or std::acos(-1) before C++20 constexpr double your_cos(double x) { double cos{1}, pow{x}; for (auto fac{1ull}, n{1ull}; n != 19; fac *= ++n, pow *= x) if ((n & 1) == 0) cos += (n & 2 ? -pow : pow) / fac; return cos; } int main() { std::cout << std::setprecision(10) << std::showpos << "Typical usage:\n" << "std::cos(pi/3) = " << std::cos(pi / 3) << '\n' << "your cos(pi/3) = " << your_cos(pi / 3) << '\n' << "std::cos(pi/2) = " << std::cos(pi / 2) << '\n' << "your cos(pi/2) = " << your_cos(pi / 2) << '\n' << "std::cos(-3*pi/4) = " << std::cos(-3 * pi / 4) << '\n' << "your cos(-3*pi/4) = " << your_cos(-3 * pi / 4) << '\n' << "Special values:\n" << "std::cos(+0) = " << std::cos(0.0) << '\n' << "std::cos(-0) = " << std::cos(-0.0) << '\n'; // error handling std::feclearexcept(FE_ALL_EXCEPT); std::cout << "cos(INFINITY) = " << std::cos(INFINITY) << '\n'; if (std::fetestexcept(FE_INVALID)) std::cout << " FE_INVALID raised\n"; }
Possible output:
Typical usage:
std::cos(pi/3) = +0.5
your cos(pi/3) = +0.5
std::cos(pi/2) = +6.123233996e-17
your cos(pi/2) = -3.373452105e-15
std::cos(-3*pi/4) = -0.7071067812
your cos(-3*pi/4) = -0.7071067812
Special values:
std::cos(+0) = +1
std::cos(-0) = +1
cos(INFINITY) = -nan
FE_INVALID raised
See also
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(C++11)
(C++11)
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computes sine (
sin(x)
)
(function) |
|
(C++11)
(C++11)
|
computes tangent (
tan(x)
)
(function) |
|
(C++11)
(C++11)
|
computes arc cosine (
arccos(x)
)
(function) |
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computes cosine of a complex number (
cos(z)
)
(function template) |
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applies the function
std::cos
to each element of valarray
(function template) |
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C documentation
for
cos
|
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