Re: Approximation

*To*: mathgroup at smc.vnet.net*Subject*: [mg116452] Re: Approximation*From*: Albert Retey <awnl at gmx-topmail.de>*Date*: Wed, 16 Feb 2011 04:33:31 -0500 (EST)*References*: <ijdoc6$fco$1@smc.vnet.net>

Hi, > Is there a way to tell Mathematica to simplify and approximate an > expression assuming things such as "R is a lot smaller than G"/ R<<G ? > If not so, how would you approach the problem? You can tell Mathematica to do what you would probably implicitly do in such a situation: rewrite to use R/G and G, expand in R/G and discard powers of R/G that you consider small enough. You should look at functions Series and Limit. Here is an example as a starting point: Limit[(R + G + Exp[R + G])/(Tan[R/G] + Cos[R/G]) /. R -> d*G, d -> 0] or if you want to keep higher orders: Series[(R+G+Exp[R+G])/(Tan[R/G]+Cos[R/G]) /. R -> d*G, {d, 0, 2}] hth, albert