Question: series expansion factor missing?

r1:=2*(1-s^2)^(1/2)*arctanh((1+s)*tanh(x)/((1-s)*(1+s))^(1/2))/((1-s)*(1+s))^(1/2)+ln((1/2)*arccosh(1/s)-x)

with x=1/2*arccosh(1/s)-beta*u

is to be calculated to the first order in u.

in fact im only interested in the first order not in the zero order.

so when applying the series I get for the first order

-beta*u/sqrt(1-s^2)

whereas by hand I get:

-beta*u*s/sqrt(1-s^2)

 I'd really appreciate some idea since Im wondering wheather Im wrong or maple :-/

 

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