int x_cor(float a, float t)
{
    float X = (a * t * t)/(1 + t * t);
    return (int)X;
}

int y_cor(float a, float t)
{
    float Y = -(a * t * t * t)/(1 + t * t);
    return (int)Y;
}

for (t = -100; t < 100; t += 0.001)
    {
        if (t == -1)
            t++;
        X = x_cor(a, t);
        Y = y_cor(a, t);
        SDL_RenderDrawPoint(renderer, X + null_X, Y + null_Y);
    }
SDL_RenderPresent(renderer);