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# std::acos

From cppreference.com
< cpp‎ | numeric‎ | math

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`.

### [edit] Parameters

arg | - | value of a floating-point or Integral type

### [edit] 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.

### [edit] 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

### [edit] See also

asin | computes arc sine (arcsin(x)) (function) [edit]
atan | computes arc tangent (arctan(x)) (function) [edit]
atan2 | arc tangent, using signs to determine quadrants (function) [edit]
cos | computes cosine (cos(x)) (function) [edit]
acos(std::complex) (C++11) | computes arc cosine of a complex number (arccos(z)) (function template) [edit]
acos(std::valarray) | applies the function std::acos to each element of valarray (function template) [edit]
C documentation for acos

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