DickeFix's channel

I would also wonder how he got that. Apparantly he assumes x is small and do a Taylor expansion 1/(1-z)=1+z+z^2+... with z=x^2/4-5*x^4/192+....I checked the result and it seems correct up to the second order at least. However, there are a lot of calculations inbetween, especially if you want such...