Thin Plate, Moment of Inertia

roeb

1. The problem statement, all variables and given/known data
Consider a thin homogeneous plate with a principal momenta of inertia. I1 along the principal axis x1, I₂ > I₁ along the principal axis x2. I₃ = I₁ + I₂.

Let the origins of the x_i x'_i systems coincide and be located at the center of mass O about an axis inclined at an angle a from the plane of the plate and perpendicular to the x₂ axis. If I₁ / I₂ = cos(2a), show that at time t the angular velocity about the x₂ axis is

w₂ = omega*cos(a)*tanh(omega*t*sin(a))


2. Relevant equations



3. The attempt at a solution

I am having a hard time starting this problem.
So we know that angular momentum and energy should be conserved, but that doesn't appear to help me at all.

I'm thinking that Euler's equations should probably be used (force free)

(I₂ - I₃)w₂w₃ - I₁w'₁ = 0

(I₃ - I₁)w₃w₁ - I₂ w'₂ = 0

(I₁ - I₂)w₁w₂ - I₃ w'₃ = 0

But plugging in I₁ = I₂*cos(2a) doesn't seem to yield anything..

Where does that tanh come from?

Anyone have any hints?