Tanh

Defined in header <cmath>.

Description

Computes the hyperbolic tangent of num. The library provides overloads of std::tanh for all cv-unqualified floating-point types as the type of the parameter num  (since C++23).
Additional Overloads are provided for all integer types, which are treated as double  (since C++11).

Declarations

C++23

// 1)
/* floating-point-type */ tanh( /* floating-point-type */ num );
// 2)
float tanhf( float num );
// 3)
long double tanhl( long double num );

Additional Overloads

// 4)
template< class Integer >
double tanh ( Integer num );

C++11

// 1)
float tanh ( float num );
// 2)
double tanh ( double num );
// 3)
long double tanh ( long double num );
// 4)
float tanhf( float num );
// 5)
long double tanhl( long double num );

Additional Overloads

// 6)
template< class Integer >
double tanh ( Integer num );

Parameters

​num - floating-point or integer value

Return value

If no errors occur, the hyperbolic sine of num (tanh(num), or (e^num + e^-num)/(e^num - e^-num)) 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, ±0 is returned If the argument is ±∞, ±1 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, and 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 Additional Overloads. They only need to be sufficient to ensure that for their argument num of integer type, std::tanh(num) has the same effect as std::tanh(static_cast<double>(num)).

Examples

#include <cmath>
#include <iostream>
#include <random>
 
double get_random_between(double min, double max)
{
    std::random_device rd;
    std::mt19937 gen(rd());
    return std::uniform_real_distribution<>(min, max)(gen);
}
 
int main()
{
    const double x = get_random_between(-1.0, 1.0);
 
    std::cout 
        << std::showpos
        << "tanh(+1) = " 
        << std::tanh(+1) << '\n'
        << "tanh(-1) = " 
        << std::tanh(-1) << '\n'
        << "tanh(x)*sinh(2*x)-cos(2*x) = "
        << std::tanh(x) * std::sinh(2 * x) - std::cosh(2 * x) << '\n'
    // special values:
        << "tanh(+0) = " 
        << std::tanh(+0.0) << '\n'
        << "tanh(-0) = " 
        << std::tanh(-0.0) << '\n';
}

Possible Result

tanh(+1) = +0.761594
tanh(-1) = -0.761594
tanh(x)*sinh(2*x)-cos(2*x) = -1
tanh(+0) = +0
tanh(-0) = -0