Prototype: double atan(double a_tan);
Header File: math.h (C) or cmath (C++)
Explanation: Acos is used to find the arctangent of a number (give it a tangent value and it will return the angle, in radians corresponding to that value). It accepts all real numbers.

//Example gives the angle corresponding to tangent 10
#include <iostream>
#include <cmath>
int main()
Other Functions