Simplification Question: Steps from First Line to Second Line

[theone]

Homework Statement

Does anyone know what was done to go from the first line to the second?

Homework Equations

The Attempt at a Solution

I don't know what sequence of steps they did after the angle was factored.
I think both sides were then multiplied by \frac{mls^2}{(M+m)(I+ml^2)} or something?

 

[gleem]

From the original equation get a common denominator, mls². for all terms. collect terms in s⁴,s³,s² and s.
write Φ/U divide the numerator and denominator by the coefficient of the s⁴ term which is q. DA DA.