When Answering This Question - I've Plugged Into M

JonnyMath

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When answering this question - I've plugged into my calculator (ti 89) and ms excel the same numbers that you have displayed in the solutions... instead of getting for part 2 step 2 or  (ii) 0.263158 and for part (iii) 0.251256 I get 0.263160 and 0.261300.   My calculator display digits mode is set to float 7... why the discrepancy and how do I fix this?  

 

Answer No.1

Anonymous

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Ah, I was thinking of the wrong question. Nevermind; whatI was thinking of wouldn't be an issue here. I can't helpyou. Sorry!

Answer No.2

Anonymous

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If it is off by only a small amount, it could be a roundingerror. On computers (and likely on the 89, though I'm unsurehere), a decimal is most often represented by the sum a_i / 2^i fori = 1 to some finite number and a_i = 1 or 0. As a result,since you are only summing powers of 2, it is impossible to get anexact solution for certain numbers (even if you have millions ofdigits). This leads to small errors. As a result, youshould never trust a computer's floating point math to more than afew digits unless the program is specifically designed forhigh-precision math (excel is not one of these programs).

Answer No.3

MisterMaster

From: US
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Votes: 93
Under "Mode" if you push F2 to get page 2, do you have "exact"under the exact/approx option?

Answer No.4

Anonymous

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How is your problem scaled? Computers have a particularlyhard time with precision in matrix inversion if the numbers in somerows are several orders of magnitude more than on another. You can divide all the numbers on the same row by 100 or 1000 orso.

Answer No.5

Anonymous

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I was saying excel might have given you the wrong answer. Ithas been known to do so.

Answer No.6

Anonymous

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I had automatic - it doesn't matter what it is on this setting - I've tried it multiple ways including using exact...   any suggestions?  

Answer No.7

Anonymous

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Ti 89's use 13 decimals.. I'm wondering why this is rounding off at5 - none of the settings seem to indicate why this would be.. I'velooked through the calculator book, but just want to be able tosolve the problem correctly with my calculator like the question inthe book asks (rounded to 6 decimal places). Can the TI-89not do this? Thanks!!!

Answer No.8

LovelyTeacher2

From: US
Posts: 38
Votes: 152
I'm not sure what you mean by scaled... I put the numbers in exactly as related in the solution for problem 3E in chapter 2.1... I plugged the equation in, and even tried to break it up into separate calculations so that the precision would not be lost.  

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