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Jun
15
comment Finding when a ODE returns to starting position
The distance has so many local minima I think you need to do this partly by hand. Plot the result and observe it looks near to zero around 39, then feed NMinimize a tight range: NMinimize[..., {t, 38.5, 39.5}].
Jun
15
comment Integrating a highly oscillatory function
It is typical for NIntegrate to have a problem discriminating between a result that is actually zero and one that us numerically very small. One thing you can do is separately integrate {x,-Pi,0} and {x,0,Pi} and add the results.
Jun
15
comment NIntegrate of surface area of intersecting spheres yields zero
make that ` 0 < Norm[ball[[1]]-#[[1]]]<2 r ` (still untested, no v10 here..)
Jun
15
comment Integrating a highly oscillatory function
Look at lower values of n, you can convince yourself the FastOscPart2 case is zero and the FastOscPart1 case is purely real. If you need to prove such you should probably take this to math.stackexchange.com.
Jun
15
comment Integrating a highly oscillatory function
It works just fine now (v9) I must say I find it bothersome that your formulation produces a vastly different result from using LevinRule with no further options. Makes me thing something is wrong with your options, but that's outside my expertise..
Jun
15
comment NIntegrate of surface area of intersecting spheres yields zero
Cant test it , but I think you need to replace Delete[ imgballs, #2] with something like Select[ imgballs , Function[{ball}, Norm[ball[[1]]-#[[1]]]<2 r]]. If that works change MapIndexed to Map as well.
Jun
15
comment Integrating a highly oscillatory function
Please copy your own code back to a clean session and verify that it runs. You've claimed to fix it several times yet still have undefined k.
Jun
15
comment Integrating a highly oscillatory function
try making b exact 3/4 ..
Jun
15
comment Integrating a highly oscillatory function
it might be worth a try to change variables so you are integrating from -n Pi to n Pi.
Jun
15
comment NIntegrate of surface area of intersecting spheres yields zero
re:latest edit. I'd assume you've hit on a special case where some spheres are just touching, or have a very small overlap.
Jun
12
comment Fitting data to a complicated function
You really should take the time to learn how to edit your question so it contains usable code. You need to take the pretty formatted matrices (DM for example) and change them back to {{lists}} before pasting to this site.
Jun
12
comment Demonstration of an arbitrarily oriented and translated ellipsoid
just neater and maybe less prone to error.. r[a_, b_, c_] = Dot @@ MapThread[RotationMatrix, { -{ c, b, a}, IdentityMatrix[3]}]. Since its not a delayed assignment there will be no effect on performance. Another small piece of advice, avoid starting your own symbols with Caps to avoid conflicts with built in functions.
Jun
12
comment Demonstration of an arbitrarily oriented and translated ellipsoid
Look into using RotationTransform and related instead of rolling your own. Also I'd suggest providing initial values for Manipulate, eg, {{d,0},-10,10,1}`
Jun
12
comment Why DSolve doesn't handle duplicate boundary condition
interesting observation, but it is just a warning. You could do Quiet@DSolve ...
Jun
12
revised Insert several rows and problem with Return
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Jun
12
revised Insert several rows and problem with Return
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Jun
12
answered Insert several rows and problem with Return
Jun
12
comment NIntegrate of surface area of intersecting spheres yields zero
related: mathematica.stackexchange.com/questions/73282/… mathematica.stackexchange.com/questions/46412/…
Jun
11
revised NIntegrate of surface area of intersecting spheres yields zero
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Jun
11
revised NIntegrate of surface area of intersecting spheres yields zero
added 251 characters in body