How to find the square root of any number?

Answer 1

Or, if you don't want to include the whole module just for the sqrt function, you might calculate it by taking it to the power of 0.5:

81**.5 = 9.0, as 9**2 = 81

Answer 2

You have to include the Math headerfile. THis includes the Math class with its sqrt(double a)-Method.
For example:
#include <iostream>
#include <Math.h>

double a, result;
a = 9.0;
result = Math.sqrt(a);
std::cout<<result;