Natural frequencies of two mass rotor system are given as
A factor 9.81 is used since 
is in Nm2 and we need in kgm2.
Figure 6.39 Equivalent two mass rotor geared system
The node location can be obtained as
which gives
The stiffness of shaft length equal to 
will be (equivalent stiffness corresponding to shaft A speed)
The shaft stiffness corresponding to shaft B speed can be defined in two ways i.e.
On equating above equations the location of the node in the actual system from disc B can be obtained as
which is same as by previous method.