[Posted by I am wathan.]
Consider forces on each mass, we get
Substitution these in above equations.
We will get
or in matrix form
This equation system has the trivial solution
We don't want the trivial solution, so that
Solve this equation, we will get four values of
in (2), so that
We will get the genaral solution (in matrix form)
In order to eliminate imagine parts of solution, let
There are three normal modes. That areFINISH
I spend very long time to type LaTex code!!!