I don't understand the light deflection calculus

[luxxio]

i am studing the book of weinberg of general relativity. in the part about light deflection weinberg perform the calculus of the angle deflection of a light ray bended bay a gravitational body. i don't how can evalute the integral. in other words i don't understand de taylor aproximation of the integral. why the integral is not divergent? how can help me to understand?

 

[mathman]

It would be easier to respond if you could explicitly show rhe integral you are talking about, including definitions of symbols.