sand15

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11 years, 29 days

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These are questions asked by sand15

This is a report of a Maple_2015's bug, apparently fixed in more recent versions, but which may have persisted for a few versions beyond 2015.
I don't think it's necessary to fill out an RCS form.

All started with an error in my code which was balanced by a maple 2015 bug. So I didn't see any error until I sent my code to @C_R  who uses a newer Maple version.
More precisely, in my Maple 2015 code I defined a NxN matrix B, a vector A of length N, that I mistakenly defined as a vector column, and finally computed the quantity R = A . B . A+.
Of course Maple should have fire an error.

The bug is that Maple 2015 doesn't fire an error if A is a float vector and B a float matrix.

restart

kernelopts(version)

`Maple 2015.2, APPLE UNIVERSAL OSX, Dec 20 2015, Build ID 1097895`

(1)

A := Vector(2, symbol=a):
B := Matrix(2$2, symbol=b):
R := A.B.A^+

Error, (in LinearAlgebra:-Multiply) cannot multiply a column Vector and a Matrix

 

A := Vector(2, i -> i):
B := Matrix(2$2, (i, j) -> i+j):
R := A.B.A^+

Error, (in LinearAlgebra:-Multiply) cannot multiply a column Vector and a Matrix

 

A := evalf(Vector(2, i -> i)):
B := evalf(Matrix(2$2, (i, j) -> i+j)):
R := A.B.A^+

30.

(2)

R := A^+.B.A

30.

(3)
 

 

Download Maple_2015_Bug.mw

At the beginning was this problem asked to 11th-12th Grade students:
 

Let C a vertical cylinder of radius RC = 10, and S a steel sphere of radius R = 4.
We place S into C and fill it with water up to the moment the water reaches the top of S.
Let V the volume of the water we used.
We then remove S and replaces it by another steel sphere S' with radius R' <> 4. Could it be that the free surface of the water reaches exactly the top of S'?
If it is so what is then the value of R'?

Mathematically does the equation (𝝅RC2) ⨯ (2R) - (4 𝝅RS3/3) = (𝝅RC2) ⨯ (2R') - (4/3 𝝅R'3), where RC = 10 and R = 4, have other strictly positive solutions than the trivial one R' = R?


The answer here is yes: R' = 5521/2 -2 ≅ 9.7473.. .

When I read this problem, I immediately asked myself the following question "Does a second sphere S' always exists whatever the values RC > 0 and R (0, RC]?".

In the attached worksheet I used two different Maple tools to answer this question:

  • firstly solve+assumptions plus plots:-inequal to visualize the (RC, R) domain where S' exists,
  • next solve/parametric to present another way to get the characterization of this same domain.

The problem is that solve+assumptions and plots:-inequal both give the same correct result but solve/parametric does not.
PlotsInequal_vs_SolveParametric.mw

For this specific problem solve/parametric fails finding the correct result.
Is that a bug or did I misuse it?

Thanks in advance

I'm not sure of the Maple function I have to use to represent the modified Bessel function of the third kind with index 1.

The Bessel function of the third kind is also named the Hankel function.

I mistakenly started to use HankelH1 or HankelH2 but quickly realized they are both complex-valued functions while the paper I'm working on uses a real-valued modified Bessel function of the third kind: finally, does this latter exist in Maple 2015?

Thanks in advance

I feel that it is increasingly common for answers to generate no reaction from their authors.

Perhaps the author simply voted up... but in that case, would it be possible to indicate this (something like "XXX voted up")? 

This would avoid wasting time responding to the same author in the future, as it doesn't seem to care about commenting the answer.


I'm struggling to construct a statistical Distribution involving Product.
This is likely a question of delayed evaluation but I'm not capable to fix it.
Can you please look to this  Product_error.mw  worksheet  and help me fixing the issue?

Thanks in advance

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