The above simulation will calculate \int_{x_i}^{x_f} f(x) dx
where f(x) can be any function of x
You need to specify the range of integration x_i,x_f
The default is f(x)=sin (a*x) to show that user can enter methematic function
However, it can be changed to f(x)=x+0.5*x*x or any other form of polynomial.