Re: About NIntegrate

*To*: mathgroup at smc.vnet.net*Subject*: [mg71400] Re: About NIntegrate*From*: "dimitris" <dimmechan at yahoo.com>*Date*: Thu, 16 Nov 2006 00:54:50 -0500 (EST)*References*: <ejf0mv$3qv$1@smc.vnet.net>

Before you start working with Mathematica you should try to LEARN it syntax. All programming languages have theis syntax rules, why you believe Mathematica is an exception? Here is good place to start: Copy/Paste the following command in a Mathematica notebook and then execute it. Here are also some things to notice: Do not mix exact and non exact numbers like 3 with 0.3; use 3/10 for example instead. For your integral the correct form of the iterator is {variable,lower limit, upper limit} Note you much treat Numerical Integration as an interactive object; for example plot the functions to be NIntegrated before you call the command. Are there any singularities in the integration range? Since you want a numerical estimate and not a symbolic result don't use Integrate; try NIntegrate in the definition of P. For users of introductory level I always suggest to avoid defining functions with Capital letters. Regards Dimitris Evanescence wrote: > Dear all: My question is as follows: > > First I definite one variable is: a=Cosh[b] > then,I definite two functions: > one is : > P[a_]=(((2)^(1/2))/Pi)*Integrate[(Cosh[I*t])/((a-Cosh[t])^^(1/2)),0,b,t] > ! (I is the (-1)^(1/2)) ,the upper limit is b, the lower limit is 0) > another > is:G[a_]=((-(a-Cos[0.5])^(-3/2))/(3*(10)^2))*(Sin[0.5])^(2)+(1/1-0.5*0.1)*((0.025*(1+Cos[0.5])+0.4/999)*(1+Cos[0.5])^(1/2)*(ArcTan[(a-Cos[0.5])^(1/2)/(1+Cos[0.5])^(1/2)]-Pi/2)+(0.025*(1-Cos[0.5])-0.4/999)*(1+Cos[0.5])^(1/2)*(ArcTanh[(1-Cos[0.5])^(1/2)/(a-Cos[0.5])^(1/2)]) > > then > NIntegrate[P[a]*G[a],{a,1,Infinity}] > but get error message is NIntegrate P[a]*G[a] is not numerical at > {a}={2.} > so,please solve my confuse,thank you! > > Evanescence 2006/11/15