std::atan,std::atanf,std::atanl (3) - Linux Manuals

std::atan,std::atanf,std::atanl: std::atan,std::atanf,std::atanl

NAME

std::atan,std::atanf,std::atanl - std::atan,std::atanf,std::atanl

Synopsis

Defined in header <cmath>
float atan ( float arg );
float atanf( float arg ); (since C++11)
double atan ( double arg ); (1) (2)
long double atan ( long double arg );
long double atanl( long double arg ); (3) (since C++11)
double atan ( IntegralType arg ); (4) (since C++11)

1-3) Computes the principal value of the arc tangent of arg
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 of a floating-point or Integral_type

Return value

If no errors occur, the arc tangent of arg (arctan(arg)) in the range [-

π
2

, +

π
2

] radians, is returned.
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 +∞, +π/2 is returned
* If the argument is -∞, -π/2 is returned
* if the argument is NaN, NaN is returned

Notes

POSIX_specifies that in case of underflow, arg 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.

Examples

// Run this code

  #include <iostream>
  #include <cmath>

  int main()
  {
      std::cout << "atan(1) = " << atan(1) << " 4*atan(1) = " << 4*atan(1) << '\n';
      // special values
      std::cout << "atan(Inf) = " << atan(INFINITY)
                << " 2*atan(Inf) = " << 2*atan(INFINITY) << '\n'
                << "atan(-0.0) = " << atan(-0.0) << '\n'
                << "atan(+0.0) = " << atan(0) << '\n';
  }

Output:

  atan(1) = 0.785398 4*atan(1) = 3.14159
  atan(Inf) = 1.5708 2*atan(Inf) = 3.14159
  atan(-0.0) = -0
  atan(+0.0) = 0