asin()

The asin() function returns the inverse sine of the argument in radians.

asin(n)

Use asin() to return the inverse sine of 0.0:

#include <iostream>
#include <cmath>

int main() {
  double x = 0.0;
  double result;

  result = std::asin(x);

  std::cout << result << " radians" << "\n";
  // Output: 1.5708 radians
}