dead on!

just show at least three terms of the summation before the ellipses

now what does it mean when there are two sigma's next to each other like #4?

the same as putting teh second one inside each term of the first summation.

you could do either first, but I think you should start with the inner... right nate??

then expand the outer summation with all the terms of the inner

right to left I spose?

yes, but in this case, there is something missing that makes this problem pretty simple.

what is it?

Yeah, that's how I'd tackle it.

Start with i = 1, then calculate the right summation, then move to i = 2...n

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that is weird.. so what it is saying

start at 1, end at n... then put that i into the next sigma as its stopping point and the output is 4+4+4+.....+4?

the inner summation does not have an indexing variable in the summation and can be written as:

4*(sum(1, j = 1 .. i)) -> this means 4 times the summation of 1, with j=1 ending at i

this gives you 4*i

in your text you should have a proof of why that is.

You should also have some common identities that often come up with their proofs.

having a single indexing variable with nothing else happening to it, is one of those identites.

perhaps you can do this problem without the identity?

there are many ways to think of that problem. My suggestion to start with the inside term is based on future problems being more difficult.

You will be taking summations and finding algebraic expressions for them based on identities.

you will want to simplify the inside terms, more often than otherwise.


----another way to look at this problem: take the 4 all the way outside to the left and replace it with 1.

what is the summation of 1 ?


this may help explain what nate is suggesting and what you were trying to explain.

-brain explodes-

we have no explanation of summation in our texts since summation is something that is supposed to be known going into cs1 apparently

http://en.wikipedia.org/wiki/Summation

here is a good list of 'identities' just to get you primed. I don't want to go too far into it if you don't need it yet. But it looks like a couple of the simpler ones may appear.

Is this calc 1? what is the last topic you will do this term?

thats weird, I didn't do any real series until calc 3....

this is for computer science 1

fukk


how well do you need to know this stuff? will be writing anything that requires it?

probably!

but you might not have to.. the program I am struggling with now has been assigned before but not assigned with recursion having to be mandatory!

I think I might cause more confusion than necessary if I try to help you with the more complicated ones that should use the series forms / identities.

There are other smarter math guys here, I'll back off and see if anyone can pick this up.

But maybe, knowing what you know now, you should try doing those problems by hand the long way without identities to get a better understanding??

if your proff said "use technology" then I can help with calculator syntax and whatnot.

I'll try the rest of the problems and keep up with the thread.