Re: About NIntegrate

*To*: mathgroup at smc.vnet.net*Subject*: [mg71419] Re: About NIntegrate*From*: "Evanescence" <origine26 at yahoo.com.tw>*Date*: Fri, 17 Nov 2006 04:30:56 -0500 (EST)*References*: <ejf0mv$3qv$1@smc.vnet.net><ejh0m2$96e$1@smc.vnet.net>

Dear Mr. Dimitris: Very thank you the suggestions that you give me. I will remember in my mind. The Function of P[a] is the integration form that cannot more simplify it ,because I will solve the NIntegrate[P[a]*G[a]] so seem to cannot NInitegrate P[a] at the first. Very thank you you look my question and answer it . Regards. Evanescence. dimitris ¼g¹D¡G > 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