Create a tutorial.cxx file with the following code:

#include <iostream>
#include <stdlib.h>
#include "MathFunctions.h"

using namespace std;

int main(int argc, char* argv[])
{
 if(argc < 2){
 cout<<"Usage: "<<argv[0]<<" number"<<endl;
 return 1;
 }
 cout<<"The sqrt of "<<argv[1]<<" is "<<mysqrt(atoi(argv[1]))<<endl;
 return 0;
}

Create a CMakeLists.txt in the same folder of tutorial.cxx with the following code:

cmake_minimum_required(VERSION 2.6)
Project(Tutorial)

include_directories("${PROJECT_SOURCE_DIR}/MathFunctions")
add_subdirectory(MathFunctions)

add_executable(Tutorial tutorial.cxx)
target_link_libraries(Tutorial MathFunctions)

Create a folder called MathFunctions and go into it:

mkdir MathFunctions && cd MathFunctions

Create a mysqrt.cxx file with the following code:

#include "MathFunctions.h"

double mysqrt(int number)
{
 if(number <=0)
 return 0;

 double delta, result;

 // do ten iterations
 for (int i = 0; i < 10; ++i) {
 if (result <= 0) {
 result = 0.1;
 }
 delta = number - (result * result);
 result = result + 0.5 * delta / result;
 }
 return result;
}

Create a MathFunctions.h file with the following code:

#include <math.h>
double mysqrt(int);

Create a CMakeLists.txt in this same folder with the following code:

add_library(MathFunctions mysqrt.cxx)

In order to keep the build files easy to remove, create a build folder by running

mkdir build && cd build

Run Cmake and then make

cmake .. && make