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## Re: [Maxima-discuss] dblquad fail

 From: address@hidden Subject: Re: [Maxima-discuss] dblquad fail Date: Fri, 29 Jul 2016 00:59:09 +0900 (JST)

```--- octave
>
> Thank you.
>
> This works:
> octave-3.6.4.exe:3>  I = dblquad(@(r,q)abs(
> r.*sqrt(r.^2+1-2*cos(2*pi*q))),0,1,0,1)
> I =  0.586626703381746
>
> ... but this doesn't:
> octave-3.6.4.exe:4>  I =
> dblquad(@(r,q)r.*sqrt(r.^2+1-2*cos(2*pi*q)),0,1,0,1)
> error: quadcc: integrand F must return a single, real-valued vector
> error: called from:
> error:   K:\OctaveVS\share\octave\3.6.4\m\general\dblquad.m at line 72,
> column 10
> error:    at line -1, column -1
> error: quadcc: integrand F must return a single, real-valued vector
> error:   K:\OctaveVS\share\octave\3.6.4\m\general\dblquad.m at line 65,
> column 5
>
> Why is the abs() necessary?
>
perhaps at report some values of r, p, the term in squere root is minus and
square root of it is imaginary and this causes error.

Tatsuro

```

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