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.