std::tan

float       tan( float arg );

double      tan( double arg );

long double tan( long double arg );

double      tan( Integral arg );

Computes the tangent of arg (measured in radians).

Parameters

Return value

If no errors occur, the tangent of arg (tan(arg)) is returned.

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.

Example

#include <iostream>
#include <cmath>
#include <cerrno>
#include <cfenv>
 
#pragma STDC FENV_ACCESS ON
const double pi = std::acos(-1);
int main()
{
    // typical usage
    std::cout << "tan  (pi/4) = " << std::tan(  pi/4) << '\n' // 45 deg.
              << "tan(3*pi/4) = " << std::tan(3*pi/4) << '\n' // 135 deg
              << "tan(5*pi/4) = " << std::tan(5*pi/4) << '\n' // -135 deg
              << "tan(7*pi/4) = " << std::tan(7*pi/4) << '\n'; // -45 deg
    // 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";
}

tan  (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

See also