133 reputation
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bio website tudelft.nl
location Delft, Netherlands
age 25
visits member for 3 months
seen May 5 at 11:23
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I am a PhD student in the field of fluid dynamics and soft matter.

profile for michielm on Stack Exchange, a network of free, community-driven Q&A sites


Apr
11
awarded  Teacher
Mar
26
awarded  Supporter
Mar
23
revised Evaluating the integral of $\cos (\theta )\cos\left[\tan ^{-1}\left(\frac{a^2 \tan (\phi )}{b^2}\right)\right]$
edited body
Mar
22
comment Evaluating the integral of $\cos (\theta )\cos\left[\tan ^{-1}\left(\frac{a^2 \tan (\phi )}{b^2}\right)\right]$
I had tried it, but it gave a very different result. However, looking at the documentation I found that I should use ArcTan[b^2 Cos[phi]],a^2 Sin[phi]] to get the correct result. Thanks! If you could write it as an answer I will definitely accept it.
Mar
22
revised Evaluating the integral of $\cos (\theta )\cos\left[\tan ^{-1}\left(\frac{a^2 \tan (\phi )}{b^2}\right)\right]$
added 258 characters in body
Mar
22
comment Evaluating the integral of $\cos (\theta )\cos\left[\tan ^{-1}\left(\frac{a^2 \tan (\phi )}{b^2}\right)\right]$
@MichaelE2 no I am sure the phase-shift is the correct thing to do. The reason is that ArcTan[(a/b)^2 Tan[[Phi]]] represents the angle the interface normal of an ellipse makes with the x-axis as determined from the angle the local x,y coordinates make with the x-axis (this angle is $\phi$). So I know that the whole thing should run from 0 to 360 deg and that the minima and maxima should coincide with those found when a=b. ---- So maybe I didn't explain enough of the background of the problem in my original question, but this is what I was looking for
Mar
21
comment Evaluating the integral of $\cos (\theta )\cos\left[\tan ^{-1}\left(\frac{a^2 \tan (\phi )}{b^2}\right)\right]$
Thanks for the explanation of how to get the answer to the integral, but I found out that it was in fact not the answer to the integral that was incorrect, but rather what I fed it: the Cos[ArcTan[ Tan[[Phi]]]] which has a modulus at $\pi/2$
Mar
21
revised Evaluating the integral of $\cos (\theta )\cos\left[\tan ^{-1}\left(\frac{a^2 \tan (\phi )}{b^2}\right)\right]$
added 4 characters in body
Mar
21
answered Evaluating the integral of $\cos (\theta )\cos\left[\tan ^{-1}\left(\frac{a^2 \tan (\phi )}{b^2}\right)\right]$
Mar
21
revised Evaluating the integral of $\cos (\theta )\cos\left[\tan ^{-1}\left(\frac{a^2 \tan (\phi )}{b^2}\right)\right]$
added 183 characters in body
Mar
21
revised Evaluating the integral of $\cos (\theta )\cos\left[\tan ^{-1}\left(\frac{a^2 \tan (\phi )}{b^2}\right)\right]$
some additional information
Mar
21
asked Evaluating the integral of $\cos (\theta )\cos\left[\tan ^{-1}\left(\frac{a^2 \tan (\phi )}{b^2}\right)\right]$
Mar
2
awarded  Autobiographer
Feb
27
awarded  Scholar
Feb
27
accepted Stop Mathematica from giving imaginary solutions
Feb
27
comment Stop Mathematica from giving imaginary solutions
@DanielLichtblau thanks for the explanation, I was not aware of that phenomenon. The Cubics->False option doesn't solve it however
Feb
26
awarded  Editor
Feb
26
comment Stop Mathematica from giving imaginary solutions
I have done what you mentioned, except for the //First//First part, because that will give me the wrong 1 of the 3 answers.
Feb
26
revised Stop Mathematica from giving imaginary solutions
A step further in the question
Feb
26
awarded  Student