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Re: get a, b from numbers in the form a+b Pi

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On 5/22/11 at 6:57 AM, rob@piovere.com (1.156) wrote:

>I have lists  of numbers (Mathematica output) all numerically in the
>form a + b*Pi and I'm trying to extract the values of a and b for
>further work.

>Here's an example of the best I've been able to do so far:

>nums={1/2 (-2+\[Pi]),-2+(3 \[Pi])/4,-(11/3)+(5 \[Pi])/4,5/48 (-64+21
>\[Pi]),-(61/5)+(63 \[Pi])/16,-(338/15)+(231 \[Pi])/32};
>{FullForm[#][[1,1]],FullForm[#][[1,2]]/\[Pi]}&/@nums

>When I run this line of code 4 of the six input numbers give me the
>{a,b} I'm looking for but the first and fourth entries fail because
>the form isn't right. Possibly I could patch this scheme to look for
>a small finite set of possibilities of input number form but I
>suspect I may a long way from attacking this problem correctly.

>Can someone offer some other ideas on how to pull this off? Many
>thanks for looking at this. Rob

This seems to work:

In[11]:= Expand[nums] /. a_ + b_ Pi :> {a, b}

Out[11]= {{-1, 1/2}, {-2, 3/4}, {-(11/3), 5/4}, {-(20/3), 35/16},
    {-(61/5), 63/16}, {-(338/15), 231/32}}

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Re: get a, b from numbers in the form a+b Pi Bill Rowe <readnews@sbcglobal.net> - 2011-05-23 10:25 +0000

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