Taylor expansion issues



Hi,

I define the following

f(psi,beta):=%e^(beta*(asin((2*psi)/%pi)-atan2(1,beta)+%pi/2))*cos(asin((2*psi)/%pi)-atan2(1,beta))

and I have issues in getting the taylor series around zero, while 
considering beta a constant.

for instance

taylor(f(psi,beta),psi,0,0);

returns

(%o69)/T/ 
(sqrt(beta^2+1)*(beta+%i)^(%i*beta)*%e^((%pi*beta)/2)*beta)/((beta^2+1)^((%i*beta)/2)*beta^2+(beta^2+1)^((%i*beta)/2))+...

where the imaginary unit is somehow weird.

Any clue?

Sergio