acos() is an inbuilt function in C++ STL and it’s the same as the inverse of cosine in maths. The acos() function returns the values in the range of [0, π] which is the angle in radians.
Syntax
acos(data_type x);
Parameters
- This function accepts one mandatory parameter x which specifies the value whose inverse of cosine needs to be computed. The parameter x can be of double, float, or long double datatype.
Note: x must be in the range of [-1, 1] to find valid output as [0, π], else acos(x) function returns NaN(Not a Number).
Return Value
- It returns angles in radians in the range of [0,π]. It is the counterclockwise angle that is measured in radians.
Examples of acos() function
Example 1:
The below C++ program demonstrates the usage of the acos() function.
// C++ program to demonstrate // the acos() function #include <bits/stdc++.h> using namespace std;
int main()
{ double x = 1.0;
// Function call to calculate acos(x) value
double result = acos (x);
cout << "acos(1.0) = " << result << " radians" << endl;
cout << "acos(1.0) = " << result * 180 / 3.141592
<< " degrees" << endl;
return 0;
} |
acos(1.0) = 0 radians acos(1.0) = 0 degrees
Example 2:
The below C++ program demonstrates the usage of the acos() function.
// C++ program to demonstrate // the acos() function #include <bits/stdc++.h> using namespace std;
int main()
{ double result;
int x = -1;
// Function call to calculate acos(x) value
result = acos (x);
cout << "acos(-1) = " << result << " radians" << endl;
cout << "acos(-1) = " << result * 180 / 3.141592
<< " degrees" << endl;
return 0;
} |
acos(-1) = 3.14159 radians acos(-1) = 180 degrees
Errors and Exceptions in acos()
- The function is designed for numerical values, hence it gives a compilation error when a string or character is passed as an argument.
- The function returns nan(Not a Number) when an out-of-domain (domain [-1,1]) number is passed as an argument.
Example 3:
The below C++ program shows the error that occurred when a string is passed as an argument to acos() function.
// C++ program to demonstrate the acos() // function errors and exceptions #include <bits/stdc++.h> using namespace std;
int main()
{ double result;
string x = "gfg" ;
result = acos (x);
cout << "acos(x) = " << result << " radians" << endl;
cout << "acos(x) = " << result * 180 / 3.141592
<< " degrees" << endl;
return 0;
} |
Output
prog.cpp:10:20: error: no matching function for call to 'acos(std::string&)' result = acos(x);
Example 4:
The below C++ program demonstrates the usage of the acos() function when arguments are x >1 or x<-1, it will give nan(not a number).
// C++ program to demonstrate the // acos() function errors and exceptions #include <bits/stdc++.h> using namespace std;
int main()
{ double x = 3.7, result;
// Function call to calculate acos(x) value
result = acos (x);
cout << "acos(3.7) = " << result << " radians" << endl;
cout << "acos(3.7) = " << result * 180 / 3.141592
<< " degrees" << endl;
return 0;
} |
acos(3.7) = nan radians acos(3.7) = nan degrees
Time Complexity: O(1)
Auxiliary Space: O(1)