I am trying to prove equations (3) given in this paper
http://users.cecs.anu.edu.au/~thush/publications/vtc_final.pdf.
The authors use taylor series to approximate function $f(q) = \left(1 + q \dfrac{w_s}{w_0}\right)^{\alpha}$.
The resulting approximation is
$f(q) = \left(1 + q \dfrac{w_s}{w_0}\right)^{\alpha} \approx exp\left(q \alpha \dfrac{w_s}{w_0} - \dfrac{1}{2} \alpha \left(q \dfrac{w_s}{w_0}\right)^2 + \dfrac{1}{3} \alpha \left(q \dfrac{w_s}{w_0}\right)^3 + \dots\right)$.
I am not able to get the same results. My result is similar but not exactly the same.
I would appreciate if someone would give a try to prove this approximation.
Thanks in advance!