SFML Fourier Series Plot

#include <SFML/Graphics.hpp>
#include <math.h>
#include <iostream> //Debugging

float rads(int);
float Calculate_Y(float,int,int,int,int);

const float pi = 3.14159;
const int L_KNOB = 1;
const int A_KNOB = 2;
const int T_KNOB = 3;
const int NIL = 0;

class Application
{

    public:

    sf::RenderWindow window;
    sf::Vector2f origin;
    sf::Event event;

    int L;
    int a;
    int t;

    Application()
    {
        window.create(sf::VideoMode(800,600,32), "Serie de Fourier");
        window.setFramerateLimit(30);
        origin.x = 75;
        origin.y = 300;
        L = 200;
        a = 5;
        t = 10;
    }

    void ChecarEventos()
    {

        while (window.pollEvent(event))
        {

            if (event.type == sf::Event::Closed)
            {
                window.close();
            }

        }

    }

};

class Grid
{

    public:

    sf::Texture grid_texture;
    sf::Sprite grid_sprite;

    Grid()
    {
        grid_texture.loadFromFile("img/grid.png");
        grid_sprite.setTexture(grid_texture);
    }

};

class Sliders
{

    public:

    int selected_knob;

    sf::Texture slider_texture;
    sf::Texture knob_texture;
    sf::Sprite L_slider_sprite;
    sf::Sprite a_slider_sprite;
    sf::Sprite t_slider_sprite;
    sf::Sprite L_knob_sprite;
    sf::Sprite a_knob_sprite;
    sf::Sprite t_knob_sprite;

    Sliders()
    {
        selected_knob = NIL;

        slider_texture.loadFromFile("img/slider.png");
        knob_texture.loadFromFile("img/knob.png");

        L_slider_sprite.setTexture(slider_texture);
        a_slider_sprite.setTexture(slider_texture);
        t_slider_sprite.setTexture(slider_texture);
        L_knob_sprite.setTexture(knob_texture);
        a_knob_sprite.setTexture(knob_texture);
        t_knob_sprite.setTexture(knob_texture);

        L_slider_sprite.setPosition(450,425);
        a_slider_sprite.setPosition(450,450);
        t_slider_sprite.setPosition(450,475);

        L_knob_sprite.setPosition(500,421);
        a_knob_sprite.setPosition(500,446);
        t_knob_sprite.setPosition(500,471);

    }

    void selectKnob(sf::RenderWindow &window)
    {

        sf::Vector2i mouse = sf::Mouse::getPosition(window);
        sf::Vector2f L_knob = L_knob_sprite.getPosition();
        sf::Vector2f a_knob = a_knob_sprite.getPosition();
        sf::Vector2f t_knob = t_knob_sprite.getPosition();

        if ((mouse.x > L_knob.x) && (mouse.x < (L_knob.x+7)) && (mouse.y > L_knob.y) && (mouse.y < (L_knob.y+15)))
        {
            selected_knob = L_KNOB;
            return;
        }
        else if ((mouse.x > a_knob.x) && (mouse.x < (a_knob.x+7)) && (mouse.y > a_knob.y) && (mouse.y < (a_knob.y+15)))
        {
            selected_knob = A_KNOB;
            return;
        }
        else if ((mouse.x > t_knob.x) && (mouse.x < (t_knob.x+7)) && (mouse.y > t_knob.y) && (mouse.y < (t_knob.y+15)))
        {
            selected_knob = T_KNOB;
            return;
        }

    }

    void Move(int knob, sf::RenderWindow &window)
    {
        sf::Vector2i mouse = sf::Mouse::getPosition(window);
        int x = mouse.x;
        int y = mouse.y;

        if (x < 455) x = 455;
        if (x > 645) x = 645;

        switch (knob)
        {
            case L_KNOB:
                L_knob_sprite.setPosition(x-3,L_knob_sprite.getPosition().y);
                break;
            case A_KNOB:
                a_knob_sprite.setPosition(x-3,a_knob_sprite.getPosition().y);
                break;
            case T_KNOB:
                t_knob_sprite.setPosition(x-3,t_knob_sprite.getPosition().y);
                break;
            default:
                break;
        }

    }


};

int main()
{
    Application app;
    Grid grid;
    Sliders sliders;

    sf::VertexArray points(sf::Points, 700);

    while (app.window.isOpen())
    {

        app.ChecarEventos();

        if (sf::Mouse::isButtonPressed(sf::Mouse::Left) && sliders.selected_knob == NIL)
        {
            sliders.selectKnob(app.window);
        }
        else if (!sf::Mouse::isButtonPressed(sf::Mouse::Left))
        {
            sliders.selected_knob = NIL;
        }

        if (sf::Mouse::isButtonPressed(sf::Mouse::Left))
        {
            sliders.Move(sliders.selected_knob,app.window);
        }

        app.L = (sliders.L_knob_sprite.getPosition().x - 300);
        app.a = (sliders.a_knob_sprite.getPosition().x - 495)*3;
        app.t = ((sliders.t_knob_sprite.getPosition().x - 490)/5);

        for (int i=0, j=0;i<app.L;i++,j++)
        {

        points[j].position = sf::Vector2f((app.origin.x + i),Calculate_Y(app.origin.y,i,app.L,app.a,app.t) );
        points[j].color = sf::Color(0,0,0);

        }

        app.window.clear(sf::Color(200,200,150));

        app.window.draw(grid.grid_sprite);

        app.window.draw(sliders.L_slider_sprite);
        app.window.draw(sliders.a_slider_sprite);
        app.window.draw(sliders.t_slider_sprite);
        app.window.draw(sliders.L_knob_sprite);
        app.window.draw(sliders.a_knob_sprite);
        app.window.draw(sliders.t_knob_sprite);

        app.window.draw(points);

        app.window.display();

    }

    return 0;

}

float rads(int degree)
{

    return degree*(3.14159/180);

}

float Calculate_Y(float origin, int x, int L, int a, int t)
{
    double Z = 0;

        for (int n = 1; n <= 100; n++)
        {

            double An = ((4 * pow(L, 2)) / pow((n * M_PI), 3)) * (1 + pow(-1, n));
            double Bn = ((4 * pow(L, 3)) / (a * pow((n * M_PI), 4))) * (1 - pow(-1, n));
            double zn = (An * cos((n * M_PI * a)/ L) * t) + (Bn * sin((n * M_PI * a)/ L) * t);

            Z = Z + ( zn * sin((n * M_PI * x) / L));
        }

    Z /= -1000;
    return origin + Z;

}