Simple pendulum - displacement increase

[ward.o.j]

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A simple pendulum of length l (supported by a light, rigid rod) is released from rest at a small angle to the upward vertical.

Show that the time taken for the angular displacement to increase by a factor of 10 is approximately (l/g)^1/2ln20.

This is from chapter 2 of Kibble. There's a section which suggests writing x=½Ae^pt+½Be^-pt as one version of the general solution to the equations of motion which seems promising, but I can't see how this leads to the value in the question, or if I'm just barking up the wrong tree.

Any advice on how to proceed would be much appreciated.

P.S. If anyone would like to shed some light for me on how to post equations so that they are more readable than the one's I've posted, I'd be grateful for that as well.

 

[fresh_42]

Please show us a little bit more than just an equation which might help. What equations have you tried so far, i.e. which was the tree you were barking at?

For on how to write formulas, you might want to read our introduction:
https://www.physicsforums.com/help/latexhelp/