what c++ library is arccos in

The arccos function in C++ is part of the <cmath> library.

To use the arccos function in C++, you need to include the <cmath> header file at the beginning of your code. This header file provides declarations for various mathematical functions, including arccos. Here is an example:

#include <cmath>

int main() {
    double x = 0.5;
    double result = std::acos(x);
    return 0;
}

In the example above, we include the <cmath> header file, declare a variable x with a value of 0.5, and then use the std::acos function to calculate the arccosine of x. The result is stored in the result variable.

The std::acos function takes a single argument of type double and returns the arccosine of the input value in radians. If you want the result in degrees, you can convert it using the std::fmod and std::abs functions. Here is an example:

#include <cmath>

int main() {
    double x = 0.5;
    double result = std::acos(x);
    double result_degrees = std::fmod(std::abs(result * 180.0 / M_PI), 360.0);
    return 0;
}

In this example, we calculate the arccosine of x using the std::acos function as before. Then, we convert the result from radians to degrees by multiplying it by 180.0 / M_PI (where M_PI is a constant defined in the <cmath> header file that represents the value of π). Finally, we use the std::fmod function to ensure that the result is in the range of 0 to 360 degrees.

I hope this helps! Let me know if you have any further questions.