need helpin solving this.

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Sg dg
Sg dg 2013-1-2
create a vector X with the elements,
http://s188.beta.photobucket.com/user/raneses88/media/exprssion_zps3b070c60.jpg.html
add up the element of the version of this vector that has 100 elements.
thanks for the help.
n= 1:100
Xn= ((-1).^n+1)/(2*n-1)
Xn =
0.0076is this correct?

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回答（3 个）

Sg dg
Sg dg 2013-1-2
yup.. for me to refer against my current answers.
  2 个评论
Image Analyst
Image Analyst 2013-1-2
编辑：Image Analyst 2013-1-2
You go first. You can do this in two lines of MATLAB code. What were they and what were your "current answers"? Then we can tell you if you were correct.
Roger Stafford
Roger Stafford 2013-1-2
As you near the end of your one hundred terms your sum ought to be oscillating roughly equal distances on either side of pi/4. Does that help?

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Sg dg
Sg dg 2013-1-2
n= 1:100
n =
Columns 1 through 21
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
Columns 22 through 42
22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42
Columns 43 through 63
43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63
Columns 64 through 84
64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84
Columns 85 through 100
85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100
>> Xn= ((-1).^n+1)/(2*n-1)
Xn =
0.0076
is this correct?
  3 个评论
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Walter Roberson
Walter Roberson 2013-1-2
The "/" operator is for matrix division. You want ./ which is element-by-element division.
Sg dg
Sg dg 2013-1-2
Xn= ((-1).^n+1)./(2*n-1)is this correct?

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Image Analyst
Image Analyst 2013-1-2
Nope. n is a vector so you need ./ rather than /.
  5 个评论
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Sg dg
Sg dg 2013-1-2
can u show me? i do nt understand by the terms.
José-Luis
José-Luis 2013-1-2
编辑：José-Luis 2013-1-2
doc sum
Example:
a = 1:10;
sum(a)

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