acos() Math Function In C++

acos() Math Function In C++ is a mathematical function that helps to find out the inverse cosine of a number.

The inverse cosine of a number in radian is computed with this function.

acos(x) = cos -1x

Syntax:

Let’s say the number is x. The syntax would be as follows:

float acos(float x);  
double acos(double x);  
long double acos(long double x);  
double acos(integral x);  

Parameter:

x: The value for which the arc cosine must be computed. It should fall between [-1,1].

Return value:

Example-1:

Let’s look at a basic case where x is higher than 1.

#include <iostream>  
#include<math.h>  
using namespace std;  
int main()  
{  
    float degree=90;  
    float x=degree*3.14/180;  
    std::cout << "Value of cosine is :" <<cos(x)<< std::endl;  
    cout<<"Inverse of cosine is :"<<acos(x);  
    return 0;  
}  

Output:

Value of cosine is :0.000796274
Inverse of cosine is :nan  

In this case, the acos() function computes the inverse cosine of an integer when x is larger than 1.

Example-2:

Let’s look at a basic case where x is equal to zero.

#include <iostream>  
#include<math.h>  
using namespace std;  
int main()  
{  
    float degree=0;  
    float x=degree*3.14/180;  
    std::cout << "Value of cosine is :" <<cos(x)<< std::endl;  
    cout<<"Inverse of cosine is :"<<acos(x);  
    return 0;  
}  

Output:

Value of cosine is :1
Inverse of cosine is :1.5708 

When the value of x is equal to zero, the acos() function computes the inverse cosine of a number.

Example-3

Let’s have a look at a basic case where x is smaller than -1.

#include <iostream>  
#include<math.h>  
using namespace std;  
int main()  
{  
    float degree= -60;  
    float x=degree*3.14/180;  
    std::cout << "Value of cosine is :" <<cos(x)<< std::endl;  
    cout<<"Inverse of cosine is :"<<acos(x);  
    return 0;  
}  

Output:

Value of cosine is :0.50046
Inverse of cosine is :nan  

In this case, the acos() function computes the inverse cosine of an integer when x is less than -1.