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 From: Doug Stewart Subject: Re: [Maxima-discuss] dblquad fail Date: Thu, 28 Jul 2016 11:57:25 -0400

On Thu, Jul 28, 2016 at 7:54 AM, Ether Jones wrote:

Thank you.

This works:
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 =
error: quadcc: integrand F must return a single, real-valued vector
error: called from:
column 10
error:    at line -1, column -1
error: quadcc: integrand F must return a single, real-valued vector
column 5

Why is the abs() necessary?

Your range of values for r and p start at zero.

if you put 0 and 0 in your eq. you get

sqrt(0^2+1-2*1)
sqrt(-1) this is imaginary

instead of abs you could try

Look at the plot of the surfase when you ask for the real part.

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