Deriving a differential equation for α from Euler equations for a rigid lamina

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PeteSampras
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"A rigid lamina (i.e. a two dimensional object) has principal moments of inertia about the centre of mass given by ##I_1=u^2-1##, ##I_2=u^2+1##, ##I_3=2u^2##

Choose the initial angular velocity to be ##ω = µN \hat{e_1} + N \hat{e_2}##. Define tan α = ω2/ω1,
which is the angle the component of ω in the plane of the lamina makes with e1. Show that it satisfies:
##\ddot{α}+ N^2 \cos α \sin α = 0##"

(the problem does not says what is N). The problem is on http://www.damtp.cam.ac.uk/user/tong/dynamics/mf3.pdf

I tried used the Euler equation, considering that ##N_1=N_2=0##

My Euler equation are:

##\dot{\omega_1}+ \omega_2 \omega_3=0##
##\dot{\omega_2}- \omega_1 \omega_3=0##
##2 \mu^2 \dot{\omega_3}+2 \omega_1 \omega_3 =N_3##

I tried of several ways of combining this equations , using that tan α = ω2/ω1, but i do not get to ##\ddot{α} + N^2 \cos α \sin α = 0##.

¿some hint please?

Some Hint to do this exercice this?...
 
I don't know whether this helps, but the first two equations imply that

x2=C sinα

x1=C cosα

where C is a constant.

Also,

x3=α'

Chet