vv

13922 Reputation

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10 years, 9 days

MaplePrimes Activity


These are replies submitted by vv

@Jason Lee 

interface(rtablesize=20);

10

(1)

A := Matrix([[4, 7, 5, 2, 6, 4, 9, 7, 5, 8, 5], [7, 7, 3, 9, 4, 5, 2, 3, 5, 6, 8], [5, 6, 5, 6, 6, 3, 7, 4, 9, 1, 9], [9, 1, 4, 8, 9, 4, 4, 2, 1, 3, 3], [5, 6, 8, 2, 2, 1, 2, 9, 5, 4, 1], [4, 7, 9, 6, 9, 2, 3, 5, 6, 3, 5], [7, 2, 5, 7, 3, 4, 9, 8, 1, 8, 9], [5, 7, 1, 2, 7, 9, 9, 2, 2, 4, 7], [1, 6, 5, 3, 9, 9, 1, 5, 7, 4, 2], [3, 7, 8, 7, 8, 3, 6, 4, 6, 9, 2]]);

_rtable[18446744074327622950]

(2)

Select the 6-th column

b:=A[..,6];

_rtable[18446744074362862038]

(3)

Select the desired columns from A

C:=A[..,[1..5,7..11]];

_rtable[18446744074362856622]

(4)

The linear system (matrix form)   C.x = b   has the solution  x = C^(-1) . b   (provided that C is not singular)

C^(-1) . b;

_rtable[18446744074362839518]

(5)

The 6-th element of the solution vector:

%[6];

63695593/46022164

(6)

Note that C is indeed nonsingular:

LinearAlgebra:-Determinant(C);

-92044328

(7)

 

 

Download linsyst.mw

@Jason Lee 

What exactly is not clear? I have used your notations.
But I just noticed that you are using Maple T.A. and I am not sure whether this works here.

@Carl Love 

Why dou you think that is is using list(rational) as a type? Of course, any type is a property.

is(list(rational), property);
   true

type(list(rational), property);
    true

Probably your notion of "proper property" is useful.

 

@_Maxim_ 

Of course is uses simplifications. It should  return FAIL much more frequently (when in doubt)  but it does not probably for "commercial" reasons; it prefers `false`. The assume facility deserves a much more careful implementation.

Surprisingly:
is(exp(1)+Pi,irrational);
    FAIL
So, it seems that is adopts a special strategy for properties which are not types.

 

Also:

is(Pi,irrational);
                              true
is(Pi^2,irrational);
                              FAIL
is(exp(1),irrational);
                              true
is(exp(1)^2,irrational);
                              FAIL
is(exp(2),irrational);
                              true

is(exp(sqrt(2)),irrational); #does not know Lindemann theorem (from 1882!)
                              FAIL

 

 

@st104290 

As you see in the example, sort itself does not alter the terms. Probably you have used some other command.
You may append assuming t>0  to that command.

@Markiyan Hirnyk 

As always you want to have the final word even when you are wrong.
But two pages earlier Fichtenholz states:  "generalized sum" (in the sense of Poisson).
He also says that actually Abel was not interested in the summation of divergent series.

Note.
In 1828 Abel wrote `Divergent series are the invention of the devil, and
it is shameful to base on them any demonstration whatsoever.'

[Abel died in 1829]

@Markiyan Hirnyk 

It is also called "power series method" or Poisson (e.g. in the Mathematical Analysis book by G.M. Fichtenholz).

 

@Markiyan Hirnyk 

Genericity is not strictly defined in Maple. There are plenty of such examples.
I don't think that the situation is going to change soon. The assume facility is too weak.
The correct answer for a real k should be:  piecewise(k<-1, 0, k=-1, 1, infinity)

 

sum(binomial(i+k,k),i=0..infinity) assuming k>-2,k<-1; #ok
                               0
sum(binomial(i+k,k),i=0..infinity) assuming k>-2,k<=-1; #wrong
                               0
sum(binomial(i-1,-1),i=0..infinity);simplify(%);
                  infinity                   
                   -----                     
                    \                        
                     )                       
                    /     binomial(i - 1, -1)
                   -----                     
                   i = 0                     
                  infinity                   
                   -----                     
                    \                        
                     )                       
                    /     binomial(i - 1, -1)
                   -----                     
                   i = 0                     
1+sum(binomial(i-1,-1),i=1..infinity);  # ok
                               1
sum(binomial(i+k,k),i=0..infinity) assuming k>=-1; # wrong
                            infinity
sum(binomial(i+k,k),i=0..infinity) assuming k>-1; # ok
                            infinity

 

 

 

@Preben Alsholm 

Probably the OP has converted somehow the numbers into "atomic" variables (via patettes or some 2d input "facilities").
Such as:

`#mn("13")` + 13;
     13+13

@Carl Love 

"<==" is obvious.

"==>" Follows from a lemma due to Birkhoff:

For each doubly stochastic matrix there is a permutation of the columns such that all the diagonal elements are nonzero.
(see Horn R. A., Johnson C. R. - Matrix Analysis. Cambridge 2013).

[Note that for our matrix M, (1/2)*M is doubly stochastic].

@acer 

I like Carl's main ingredient which is worth formulating explicitely:

Lemma.
A binary square matrix M has two ones in each line and each column iff
there exist a permutation matrix P and a dearangenent matrix Q such that M = (I + Q).P
(the representation is not unique).

 

 

@Carl Love 

and vote up, of course!

P.S.  Probably    runtime + time(algorithm)  >>  time(brute force)   in this case   :-)
 

@Preben Alsholm 

In other cases an error appears:

evalf(Int(1/t^2, t=I .. I*infinity));
Error, (in evalf/int) non-numeric integration limit encountered

so, probably the parameters are not correctly checked.
But anyway evalf should transform correctly the complex limits into reals.

@acer 

Just curious: is there a situation where ':-base' is really necessary instead of simply 'base'?
I cannot imagine such a possibility for name parameters.

@rlopez 

For presentations the situation is clear - use 2d input.
But for OP's specific manipulations, would you really recommend 2d input?

 

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