I was going the derivations for Fresnel zone radius approximation, and there was a jump in the math which I don't fully understand. If someone could take a look at this and help me figure. I was hinted that it had to do with the binomial theorem, but I have no idea >.<(adsbygoogle = window.adsbygoogle || []).push({});

Seems like LaTeX isn't working -_-

(D^2 + r^2)^(1/2)

if r << D

( D^2( 1 + (r^2)/(D^2) ) )^(1/2)

D1 + (r^2)/(2D^2) <--- ???

.

.

.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Binomial Identities?

**Physics Forums | Science Articles, Homework Help, Discussion**