I have an expression like this:
sum(product(xi,i,1,n)/n!,n,2,5)
which I'd like to expand to obtain a polynomial in x. But try as I might, all I can see (in the Main screen) is a symbolic representation of the sum or products, I can't get the ClassPad to expand it all out. How can I do this? ("expand" doesn't seem to have any effect here).
Thanks!
Expanding Sums, Products, Containing Variables?
Started by
AussieGuy
, Apr 03 2013 02:25 PM
classpad 330 sum product symbolic
5 replies to this topic
#1
Posted 03 April 2013  02:25 PM
#2
Posted 03 April 2013  04:20 PM
i think that you can not expand a sum( or product(
#3
Posted 03 April 2013  06:57 PM
Really? Why on earth not? That seems like a bizarre restriction. What options are there  are there alternatives to sum & product which are expandable?
#4
Posted 03 April 2013  09:31 PM
I I have not really explored (in detail) the cas system that classpad have. The quick tests that i do i could not do it.
There is a Σ in math keys, test it.I dont know if work like sum( .
There is a Σ in math keys, test it.I dont know if work like sum( .
Edited by helder7, 03 April 2013  09:32 PM.
#5
Posted 03 April 2013  11:11 PM
Σ and sum are the same. I have discovered a solution though: put the objects to be summed into a sequence:
seq(∏(xi,i,1,n)/n!,n,1,5) => s
Then add the sequence:
sum(s)
I don't know why Σ doesn't work directly.
seq(∏(xi,i,1,n)/n!,n,1,5) => s
Then add the sequence:
sum(s)
I don't know why Σ doesn't work directly.
#6
Posted 17 May 2013  07:11 PM
Maybe CP uses some kind of lazy evaluation or something in Σ and Π functions that prevents it from expanding the inner products.
Anyway yes this is a very silly limitation, at least there should be a way to force it to expand the inner product, but I couldn't find any.
Define sum2(e,x,a,b)=sum(seq(e,x,a,b)) and using this sum2 function instead of the original Σ function may help in this situation.
Anyway yes this is a very silly limitation, at least there should be a way to force it to expand the inner product, but I couldn't find any.
Define sum2(e,x,a,b)=sum(seq(e,x,a,b)) and using this sum2 function instead of the original Σ function may help in this situation.
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