std::tan,std::tanf,std::tanl(3)

NAME
std::tan,std::tanf,std::tanl - std::tan,std::tanf,std::tanl

Synopsis
   Defined in header <cmath>
   float tan ( float arg );
   float tanf( float arg ); (since C++11)
   double tan ( double arg ); (1) (2)
   long double tan ( long double arg );
   long double tanl( long double arg ); (3) (since C++11)
   double tan ( IntegralType arg ); (4) (since C++11)
   1-3) 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 (until C++11)
   is large
   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); // 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

See also
   sin
   sinf computes sine (\({\small\sin{x} }\)sin(x))
   sinl (function)
   (C++11)
   (C++11)
   cos
   cosf computes cosine (\({\small\cos{x} }\)cos(x))
   cosl (function)
   (C++11)
   (C++11)
   atan
   atanf computes arc tangent (\({\small\arctan{x} }\)arctan(x))
   atanl (function)
   (C++11)
   (C++11)
   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)