Our final codes are:

A general code, where the size of every variable can differ each time that the program runs:

//  Created by Enrique Daniel Saldivar Carranza A01225963 and Fernanda Cano A00226352 on 16/11/15.
//  Copyright © 2015 Enrique Daniel Saldivar Carranza and Fernanda Cano. All rights reserved.
//  General code where the size of every variable can differ each time that the program runs

#include <iostream>
#include <cmath>
#define pi 3.14159265359
using namespace std;
char x;
double Ax,Ay,Bx,By,Cx,Cy, lmc, lmp, lop, w, h;

void calc_length (double a, double b, double c){
    double scale, loc;
    scale= a/b; //We get how many centimeters a pixels is
    loc= c*scale;
    cout<<"The length of your object is of: "<<loc<<" cm. "<<loc*0.39370079<<" inches.";
}

void calc_angle (double ax, double ay, double bx, double by, double cx, double cy){
    double magnitud_AB, magnitud_AC, prod_punt, angle;
    magnitud_AB= sqrt(pow((Bx-Ax),2) + pow((By-Ay),2));
    magnitud_AC= sqrt(pow((Cx-Ax),2)+ pow((Cy-Ay),2));
    prod_punt=((Bx-Ax)*(Cx-Ax))+((By-Ay)*(Cy-Ay));
    angle= acos(prod_punt/(magnitud_AB * magnitud_AC));
    cout<<"The interior angle in radians is: "<<angle<<", in degrees: "<<(angle*180)/pi<<endl;
    cout<<"The exterior angle in radians is: "<<(2*pi)- angle<<", in degrees: "<<360-((angle*180)/pi)<<endl;
    // You could get an error if when calculating the angle using the product point you get 0 in the denominator or if your numerator is bigger than your denominator (calculating the arccos of a number greater than 1)
}

int main() {
    cout<<"I give the lengths of an object in centimeters and inches, or angles in radians and degrees. All of these using a digital picture (with a marker information if you want lengths)."<<endl<<endl;
    cout<<"Do you want to get angles? (type 'a'), do you want to get a length? (type 'l') ";
    cin>>x;
    while((x!='a')&&(x!='A')&&(x!='l')&&(x!='L')){
        cout<<"You did not type a valid character. Do you want to get angles? (type 'a'), do you want to get a length? (type 'l')? ";
        cin>>x;
    }
    if ((x=='a')||(x=='A')){
        cout<<"Give me the coordinates of point A (where the two lines intersect)"<<endl;
        cout << "x:";
        cin >> Ax;
        cout << "y:";
        cin >> Ay;
        cout<<"Give me the coordinates of point B: "<<endl;
        cout << "x:";
        cin >> Bx;
        cout << "y:";
        cin >> By;
        cout<<"Give me the coordinates of point C:"<< endl;
        cout<<"x:";
        cin>>Cx;
        cout << "y:";
        cin >>Cy;
        calc_angle (Ax,Ay,Bx,By,Cx,Cy);
    }
    else if ((x=='l')||(x=='L')){
        cout<<"What is the resolution of the image:\n";
        cout<<"W: ";
        cin>>w;
        cout<<"H: ";
        cin>>h;
        cout<<"Tell me the length of your marker (in cm.): ";
        cin>>lmc;
        cout<<"Tell me the length of your marker (in pixels): ";
        cin>>lmp;
        cout<<"Tell me the length of your object (in pixels): ";
        cin>>lop;
        while(((lmp>=w)&&(lmp>=h))||((lop>=w)&&(lop>=h))){
            cout<<"You are giving a pixel size of one of your objects bigger than your actual image, the objects you want to measure MUST be inside the image.\n";
            cout<<"Tell me again the length of your marker (in pixels): ";
            cin>>lmp;
            cout<<"Tell me again the length of your object (in pixels): ";
            cin>>lop;
        }
        calc_length(lmc, lmp, lop);
    }
   
    return 0;
}


An ideal conditions code, where we put as constants the values for the variables that we discovered worked better in our environment: 

//
//  main.cpp
//  Complete_specified
//
//  Created by Enrique Daniel Saldivar Carranza A01225963 and Fernanda Cano A00226352 on 16/11/15.
//  Copyright © 2015 Enrique Daniel Saldivar Carranza and Fernanda Cano. All rights reserved.
//  ideal conditions code, where we put as constants the values for the variables that we discovered worked better in our environment

#include <iostream>
#include <cmath>
#define pi 3.14159265359
#define scale 0.0441176 // This is an average of the scale in the experiments we did were 1cm::0.0441176 pixels
using namespace std;
char x;
double Ax,Ay,Bx,By,Cx,Cy, lop;

void calc_length (double a){
    double loc;
    loc= a*scale;
    cout<<"The length of your object is of: "<<loc<<" cm. "<<loc*0.39370079<<" inches."<<endl;
    cout<<"There can be an %error around 4%";
}

void calc_angle (double ax, double ay, double bx, double by, double cx, double cy){
    double magnitud_AB, magnitud_AC, prod_punt, angle;
    magnitud_AB= sqrt(pow((Bx-Ax),2) + pow((By-Ay),2));
    magnitud_AC= sqrt(pow((Cx-Ax),2)+ pow((Cy-Ay),2));
    prod_punt=((Bx-Ax)*(Cx-Ax))+((By-Ay)*(Cy-Ay));
    angle= acos(prod_punt/(magnitud_AB * magnitud_AC));
    cout<<"The interior angle in radians is: "<<angle<<", in degrees: "<<(angle*180)/pi<<endl;
    cout<<"The exterior angle in radians is: "<<(2*pi)- angle<<", in degrees: "<<360-((angle*180)/pi)<<endl;
    // You could get an error if when calculating the angle using the product point you get 0 in the denominator or if your numerator is bigger than your denominator (calculating the arccos of a number greater than 1)
}

int main() {
    cout<<"I give the lengths of an object in centimeters and inches, or angles in radians and degrees. All of these using information from a digital picture ."<<endl<<endl;
    cout<<"Do you want to get angles? (type 'a'), do you want to get a length? (type 'l') ";
    cin>>x;
    while((x!='a')&&(x!='A')&&(x!='l')&&(x!='L')){
        cout<<"You did not type a valid character. Do you want to get angles? (type 'a'), do you want to get a length? (type 'l')? ";
        cin>>x;
    }
    if ((x=='a')||(x=='A')){
        cout<<"Give me the coordinates of point A (where the two lines intersect)"<<endl;
        cout << "x:";
        cin >> Ax;
        cout << "y:";
        cin >> Ay;
        cout<<"Give me the coordinates of point B: "<<endl;
        cout << "x:";
        cin >> Bx;
        cout << "y:";
        cin >> By;
        cout<<"Give me the coordinates of point C:"<< endl;
        cout<<"x:";
        cin>>Cx;
        cout << "y:";
        cin >>Cy;
        calc_angle (Ax,Ay,Bx,By,Cx,Cy);
    }
    else if ((x=='l')||(x=='L')){
        cout<<"You have to take the picture with a camera of resolution 2448 x 3264 pixels, and you have to take the picture 1 meter away from the object (in order to get better results)."<<endl;
        cout<<"Tell me the length of your object (in pixels): ";
        cin>>lop;
        calc_length (lop);
    }
   
    return 0;
}


A "without marker" code, where with the discoveries that we made with the experiments, we were able to take the marker out, and now you just need to give the distance from where the picture was taken as an input:

//  Created by Enrique Daniel Saldivar Carranza A01225963 and Fernanda Cano A00226352 on 16/11/15.
//  Copyright © 2015 Enrique Daniel Saldivar Carranza and Fernanda Cano. All rights reserved.
//  without marker" code, where with the discoveries that we made with the experiments, we were able to take the marker out, and now you just need to give the distance from where the picture was taken as an input

#include <iostream>
#include <cmath>
#define pi 3.14159265359
#define constant 0.04194745389 //relation between scale and meter from a resolution of 2448 x 3264 pixels
using namespace std;
char x;
double Ax,Ay,Bx,By,Cx,Cy, d, op;

void calc_length (double a, double b){
    double size;
    size= constant*a*b;
    cout<<"The length of your object is of: "<<size<<" cm. "<<size*0.39370079<<" inches."<<endl;
    cout<<"There can be a %Error around 5%, the %Error decreases as you get closer to 2 m.";
}

void calc_angle (double ax, double ay, double bx, double by, double cx, double cy){
    double magnitud_AB, magnitud_AC, prod_punt, angle;
    magnitud_AB= sqrt(pow((Bx-Ax),2) + pow((By-Ay),2));
    magnitud_AC= sqrt(pow((Cx-Ax),2)+ pow((Cy-Ay),2));
    prod_punt=((Bx-Ax)*(Cx-Ax))+((By-Ay)*(Cy-Ay));
    angle= acos(prod_punt/(magnitud_AB * magnitud_AC));
    cout<<"The interior angle in radians is: "<<angle<<", in degrees: "<<(angle*180)/pi<<endl;
    cout<<"The exterior angle in radians is: "<<(2*pi)- angle<<", in degrees: "<<360-((angle*180)/pi)<<endl;
    // You could get an error if when calculating the angle using the product point you get 0 in the denominator or if your numerator is bigger than your denominator (calculating the arccos of a number greater than 1)
}

int main() {
    cout<<"I give the lengths of an object in centimeters and inches, or angles in radians and degrees. All of these using information from a digital picture."<<endl<<endl;
    cout<<"Do you want to get angles? (type 'a'), do you want to get a length? (type 'l') ";
    cin>>x;
    while((x!='a')&&(x!='A')&&(x!='l')&&(x!='L')){
        cout<<"You did not type a valid character. Do you want to get angles? (type 'a'), do you want to get a length? (type 'l')? ";
        cin>>x;
    }
    if ((x=='a')||(x=='A')){
        cout<<"Give me the coordinates of point A (where the two lines intersect)"<<endl;
        cout << "x:";
        cin >> Ax;
        cout << "y:";
        cin >> Ay;
        cout<<"Give me the coordinates of point B: "<<endl;
        cout << "x:";
        cin >> Bx;
        cout << "y:";
        cin >> By;
        cout<<"Give me the coordinates of point C:"<< endl;
        cout<<"x:";
        cin>>Cx;
        cout << "y:";
        cin >>Cy;
        calc_angle (Ax,Ay,Bx,By,Cx,Cy);
    }
    else if ((x=='l')||(x=='L')){
        cout<<"You need you to take the picture using a camera with a resolution of 2448 x 3264 pixels, and I need to know the distance from where the picture was taken, as well as the size of the object in pixels."<<endl;
        cout<<"Distance from where the picture was taken (in m.): ";
        cin>>d;
        cout<<"Size of the object in pixels: ";
        cin>>op;
        calc_length (d, op);
    }
   
    return 0;
}