The acos() function in C++ computes the inverse cosine (arccos) of a value ranging from -1 to 1. It is defined in <cmath>. Example:

cpp
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#include <iostream>
#include <cmath>

int main() {
double x = 0.7;
double result = acos(x);
std::cout << "acos(" << x << ") = " << result << " radians" << std::endl;
return 0;