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MathGroup Archive 2006

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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


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