Question form Peskin Schroeder

[Sombrero]

Sorry for bothering...
How does righthand side of formula 5.94 is derived from its left handside after some approximation?
Probably it is very simple question but I could't get that expression

Thank u very much

 

[George Jones]

Using e^2 = 16 \pi^2 \alpha^2, the left side is

\frac{2 \pi \alpha^2}{4E^2 + 4E \omega cos \theta}.

Now use an exact expression for E^2 and a two-term approximation to E to get the right side.