Re: multiintegral and table

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• Subject: [mg131650] Re: multiintegral and table
• From: "Dr. Wolfgang Hintze" <weh at snafu.de>
• Date: Sun, 15 Sep 2013 07:09:47 -0400 (EDT)
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```Am Samstag, 14. September 2013 11:48:39 UTC+2 schrieb Parada Hutauruk:
> Dear all,
>
>
>
> I have a function
>
>
>
> f_1 [x_,y_] = Integrate[2*y + x^2, {x,0,1},{y,0,x}]
>
>
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> f_2 [x_,y_,Q_] = Integrate[2*y +x^2*Q, {x,0,1},{y,0,x}]
>
>
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> f_total [x_,y_,Q_] = f_1[x,y] + f_2[x,y,Q]
>
>
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> Then I want to plot the f total using table with Q start from 0 to 10 with increment 0.0025.
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> I have defined by
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> dataxx = Table[{Q,f_total[x,y,Q]}, {Q, 0,10, 0.0025}]
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>
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> And Plot the data on the table by
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>
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> ListPlot[dataxx]
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> But when I evaluate the function, it took a long time and the plot is not yielded. Could anyone help me please to find the bug? I really appreciate for help.
>
>
>
> Thanks,
>
> PTPH

It's a simple syntax problem: "underline" is a reseerved Symbol im Mathematica (by the way, a very important one!); you must not use "underline" in a variable name.

Hence your code corrected in this respect works fine:

In[1]:= f1[x_, y_] = Integrate[2*y + x^2, {x, 0, 1}, {y, 0, x}]
f2[x_, y_, Q_] = Integrate[2*y + x^2*Q, {x, 0, 1}, {y, 0, x}]
ftotal[x_, y_, Q_] = f1[x, y] + f2[x, y, Q]

Out[1]= 7/12

Out[2]= 1/3 + Q/4

Out[3]= 11/12 + Q/4

(* in the following line I have reduce the number of terms putting the step = 1*)
In[9]:= dataxx = Table[{Q, ftotal[x, y, Q]}, {Q, 0, 10}]

Out[9]= {{0, 11/12}, {1, 7/6}, {2, 17/12}, {3, 5/3}, {4, 23/12}, {5,
13/6}, {6, 29/12}, {7, 8/3}, {8, 35/12}, {9, 19/6}, {10, 41/12}}

Regards,
Wolfgang

```

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