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#2 2012-10-17 00:32:17
- bobbym
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Re: Product of elementary matrices
Hi;
I am getting:
which can be inverted.
In mathematics, you don't understand things. You just get used to them.
Probability is the most important concept in modern science, especially as nobody has the slightest notion what it means.
90% of mathematicians do not understand 90% of currently published mathematics.
#4 2012-10-17 03:28:19
- bobbym
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Re: Product of elementary matrices
Hi;
Your mistake is in line 3. Check how you multiplied those matrices.
In mathematics, you don't understand things. You just get used to them.
Probability is the most important concept in modern science, especially as nobody has the slightest notion what it means.
90% of mathematicians do not understand 90% of currently published mathematics.
#7 2012-10-17 04:04:49
- bob bundy
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Re: Product of elementary matrices
hi Deon588
Your inverses are correct, so then you need to do the multiplying.
(AB)C = A(BC) for matrices so you have a choice of which pair you multiply first. But you must preserve order.
eg if AB = D you then do DC not CD.
I'm going to do these both ways in case I choose the way you didn't (if you see what mean)
or
Bob
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
#8 2012-10-17 04:12:02
- bob bundy
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Re: Product of elementary matrices
and you should find that inverse A = E3.E2.E1
This would be a good check that you have inv A right and that your multiplying is OK.
Bob
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
#10 2012-10-17 22:10:27
- bobbym
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Re: Product of elementary matrices
Hi Deon588;
Always break a big problem down into smaller pieces that you know how to do. This top down design is very common in programming. You knew how to do 2 matrices.
In mathematics, you don't understand things. You just get used to them.
Probability is the most important concept in modern science, especially as nobody has the slightest notion what it means.
90% of mathematicians do not understand 90% of currently published mathematics.
#11 2012-10-17 23:39:52
- bob bundy
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Re: Product of elementary matrices
hi Deon588
I know the rule for multiplying two matrices. I dareay you could devise a rule for three but it would be hard to remember. So two at a time is simplest.
You shouldn't assume that matrices can be swopped around like numbers but associativity { (AB)C = A(BC) } does work.
Beware: commutativity doesn't. { AB ≠ BA }
Did you try my practice suggestion?
and you should find that inverse A = E3.E2.E1
This would be a good check that you have inv A right and that your multiplying is OK.
Bob
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
