Expanding Equations: Simplifying 1/(x√(1-2cosθ/x)) for Higher Order Solutions

[rockstar101]

Homework Statement

Hello,
I'm in the middle of a question and I need to expand

1/(x√(1-2cosθ/x)) in powers 1/x up to order of 1/x^3

Homework Equations

The Attempt at a Solution

This is my attempt to the more complicated question.
To get to the final answer, I need to know how to expand the above question.
I've simplified to 1/(x√(1-2cosθ/x)).
now... do I use taylor expansion? But I'm not give Ao or Xo thus I can't have (X-Xo)

Please! Any help would be really appreciated! Thank you.

 

[tiny-tim]

Hi rockstar101!

Hint: what is the expansion of 1/√(1 -a) in terms of a?