# std::tan

From cppreference.com
< cpp‎ | numeric‎ | math

Defined in header `<cmath>` |  |
float tan( float arg ); | (1) |
double tan( double arg ); | (2) |
long double tan( long double arg ); | (3) |
double tan( Integral arg ); | (4) | (since C++11)

Computes the tangent of `arg` (measured in radians).

4) A set of overloads or a function template accepting an argument of any integral type. Equivalent to 2) (the argument is cast to double).

### Parameters

arg | - | value representing angle in radians, of a floating-point or Integral type

### Return value

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

The result may have little or no significance if the magnitude of `arg` 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.

### Example

Run this code

    #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";
    }

Possible output:

    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

sin | computes sine (sin(x)) (function)
cos | computes cosine (cos(x)) (function)
atan | computes arc tangent (arctan(x)) (function)
tan(std::complex) | computes tangent of a complex number (tan(z)) (function template)
tan(std::valarray) | applies the function std::tan to each element of valarray (function template)
C documentation for tan

Retrieved from "http://en.cppreference.com/mwiki/index.php?title=cpp/numeric/math/tan&oldid=73248"