I am studying the problem in Vibration effects. I would like to obtain the simplified equation of motion in (2.7).
\[Lambda] =Sqrt[l^2 + a^2 (3 Cos[\[Phi]] - Sqrt Sin[\[Phi]])];\[Lambda]ang = Simplify[\[Lambda] /. \[Phi] -> \[Theta] + 5/6 Pi]
h = Sqrt[ l^2 - 2 a^2 (1 - Cos[\[Phi]])]; hang = Simplify[h /. \[Phi] -> \[Theta] + 5/6 Pi]
Elastic energy in (2.3) can be written as:
U = 3/2 k (\[Lambda]ang - \[Lambda]n)^2
How can I write the Kinetic energy in (2.4)? Moreover, How can I write the equations in (2.5) and (2.6)?