# summation question

by joshmccraney
Tags: summation
 P: 229 hey pf! can someone explain to me what to do if presented with an equation like this: $$\sum_{i=1}^{n}A_i=i$$ is this identical to stating $A_i=i$? either way, can you please explain. thanks! josh
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P: 21,081
 Quote by joshmccraney hey pf! can someone explain to me what to do if presented with an equation like this: $$\sum_{i=1}^{n}A_i=i$$ is this identical to stating $A_i=i$? either way, can you please explain. thanks! josh
It doesn't make much sense to me. On the left side, i is an index variable that takes on the values 1, 2, 3, ..., n, so I have no idea what it means on the right side.

Where did you see this? If it's from a textbook, can you post a picture?
 Engineering Sci Advisor HW Helper Thanks P: 6,388 Just taking it at face value, it means ##A_1 + A_2 + \cdots + A_n = i## The ##i## in the sum is a "bound variable" or "dummy variable". You could replace it by anything else (except ##n##) without changing the meaning. The ##i## on the right hand side means ##i##. But using ##i## twice in one equation like that is horrible, as Mark44 said. It would have been more literate to write something like $$\sum_{k=1}^n A_k = i$$
P: 229

## summation question

yea, i was trying to generalize for determining the fourier coefficients. i have a link here on pf: http://www.physicsforums.com/showthread.php?t=733877
my question there has been answered, but if you're curious to this type of problem, there's the link.

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