Permanent of a matrix is quite similar to that of determinant, though determinant can be found in polynomial time, while permanent is #P-complete (meaning that if you solve it, you can count the number of solution of all NP problem.)

In this paper, I am going to describe a new method to calculate permanent based on a very simple principle: ...

In this How-to, I would like to demostrate how to use Lagrangian formulation for system with non-conservative force. The problem that I am going to solve is a particle on a cone (or any landscape with height which depends on the distance from the origin). It will be subjected to resistance which is proportional to it's velocity.

I will first ...

In this tutorial, I will first introduce what differential equation is. Separable first order differential equation will be solved. Then the integrating factor will be taught to solve linear differential equation of the first degree. The auxiliary equation (or characteristic equation) will be introduced to solve homogeneous linear equations, and then operator method will be taught finally to solve non-homogeneous linear equations. ...