std::tan, std::tanf, std::tanl

Defined in header `<cmath>`
	(1)
float tan ( float num ); double tan ( double num ); long double tan ( long double num );			(until C++23)
/* floating-point-type / tan ( / floating-point-type */ num );			(since C++23) (constexpr since C++26)
float tanf( float num );		(2)	(since C++11) (constexpr since C++26)
long double tanl( long double num );		(3)	(since C++11) (constexpr since C++26)
Additional overloads (since C++11)
Defined in header `<cmath>`
template< class Integer > double tan ( Integer num );		(A)	(constexpr since C++26)

1-3) Computes the tangent of num (measured in radians). The library provides overloads of std::tan 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 tangent of num ( $tan(num)$ ) 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, it is returned unmodified.
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 (to which C++ defers), but it is defined as a domain error in POSIX.

The function has mathematical poles at $π(1/2 + n)$ ; however no common floating-point representation is able to represent π/2 exactly, thus there is no value of the argument for which a pole error occurs.

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::tan(num) has the same effect as std::tan(static_cast<double>(num)).

Example

Run this code

#include <cerrno>
#include <cfenv>
#include <cmath>
#include <iostream>
 
// #pragma STDC FENV_ACCESS ON
const double pi = std::acos(-1); // or C++20's std::numbers::pi
 
int main()
{
    // typical usage
    std::cout << "tan(1*pi/4) = " << std::tan(1*pi/4) << '\n' // 45°
              << "tan(3*pi/4) = " << std::tan(3*pi/4) << '\n' // 135°
              << "tan(5*pi/4) = " << std::tan(5*pi/4) << '\n' // -135°
              << "tan(7*pi/4) = " << std::tan(7*pi/4) << '\n'; // -45°
 
    // special values
    std::cout << "tan(+0) = " << std::tan(0.0) << '\n'
              << "tan(-0) = " << std::tan(-0.0) << '\n';
 
    // error handling
    std::feclearexcept(FE_ALL_EXCEPT);
 
    std::cout << "tan(INFINITY) = " << std::tan(INFINITY) << '\n';
    if (std::fetestexcept(FE_INVALID))
        std::cout << "    FE_INVALID raised\n";
}

Possible output:

tan(1*pi/4) = 1
tan(3*pi/4) = -1
tan(5*pi/4) = 1
tan(7*pi/4) = -1
tan(+0) = 0
tan(-0) = -0
tan(INFINITY) = -nan
    FE_INVALID raised

Compiler support
Freestanding and hosted
Language
Standard library
Standard library headers
Named requirements
Feature test macros (C++20)
Language support library
Concepts library (C++20)
Metaprogramming library (C++11)
Diagnostics library
General utilities library
Strings library
Containers library
Iterators library
Ranges library (C++20)
Algorithms library
Numerics library
Localizations library
Input/output library
Filesystem library (C++17)
Regular expressions library (C++11)
Concurrency support library (C++11)
Execution support library (C++26)
Technical specifications
Symbols index
External libraries

sinsinfsinl (C++11)(C++11)	computes sine (\({\small\sin{x}}\) $sin(x)$ ) (function)
coscosfcosl (C++11)(C++11)	computes cosine (\({\small\cos{x}}\) $cos(x)$ ) (function)
atanatanfatanl (C++11)(C++11)	computes arc tangent (\({\small\arctan{x}}\) $arctan(x)$ ) (function)
tan(std::complex)	computes tangent of a complex number (\({\small\tan{z}}\) $tan(z)$ ) (function template)
tan(std::valarray)	applies the function std::tan to each element of valarray (function template)
C documentation for tan