std::acos

 

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Defined in header <cmath>
float       acos( float arg );
double      acos( double arg );
long double acos( long double arg );
double      acos( Integral arg );		(since C++11)

Computes arc cosine of arg.

Parameters

arg

-

value of a floating-point or Integral type

Return value

Arc cosine of arg in radians in the range of [0; π] radians.

Domain error occurs if arg is outside the range [-1.0; 1.0]. NAN is returned in that case.

Example

Run this code

#include <cmath>
#include <iostream>
 
int main()
{
    std::cout << "The number pi is " << std::acos(-1) << '\n';
}

Output:

The number pi is 3.14159

See also

asinasinfasinl (C++11)(C++11)	computes arc sine (\({\small\arcsin{x}}\)arcsin(x)) (function)
atanatanfatanl (C++11)(C++11)	computes arc tangent (\({\small\arctan{x}}\)arctan(x)) (function)
atan2atan2fatan2l (C++11)(C++11)	arc tangent, using signs to determine quadrants (function)
coscosfcosl (C++11)(C++11)	computes cosine (\({\small\cos{x}}\)cos(x)) (function)
acos(std::complex) (C++11)	computes arc cosine of a complex number (\({\small\arccos{z}}\)arccos(z)) (function template)
acos(std::valarray)	applies the function std::acos to each element of valarray (function template)
C documentation for acos