Page 2 - [C] sum of the series - loop?

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#16

October 25th, 2009, 04:01 PM

sizablegrin

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You actually have to know what you are doing. No instructor and no good grade can guarantee that. Only thinking well can guarantee that. If that doesn't fit your profile, you should look for another field. The programming ranks are already filled with costly failures.

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#17

October 25th, 2009, 04:06 PM

jacus

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What the hell are you talking about? I've already posted a question.

#18

October 25th, 2009, 04:13 PM

sizablegrin

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I'm talking about for real. You're talking about faking it with limited knowledge.

#19

October 25th, 2009, 04:16 PM

jacus

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OK.

If anyone feels that they can help me with my program, I'll appreciate it.

#20

October 25th, 2009, 04:22 PM

Nyan

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Isn't your code working ? I think you forgot that the sign is altering. ?

#21

October 25th, 2009, 04:23 PM

jacus

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Yes, it is.

Do you mean switching

Code:

element=(sin(n*x))/pow(n,3);

Code:

element=(sin(n*x)*pow(-1,n))/pow(n,3);

#22

October 25th, 2009, 04:32 PM

Nyan

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You are incrementing n before calculating element. Shouldn't it be after ?

#23

October 25th, 2009, 04:38 PM

jacus

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Yep. So switch

Code:

n=n+1;
    element=(sin(n*x))/pow(n,3);

Code:

element=(sin(n*x))*pow(-1,n)/pow(n,3);
n=n+1;

#24

October 25th, 2009, 05:25 PM

jwdonahue

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Because you are using pow(), you should probably use doubles, not floats. Other than that and the inconsistent use of indentation, it looks like you got most of the algorithm down. I just have one question regarding this loop conditional:

(element > 1e-8 || element < -1e-8)

What is the meaning of (element == 1e-8 || element == -1e-8) ? I am not saying this is wrong, I was just wondering what logic led you to use these magic numbers to terminate your loop?

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#25

October 25th, 2009, 05:44 PM

jacus

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Quote:

Originally Posted by jwdonahue

(element > 1e-8 || element < -1e-8)

To be frankly - I have no idea.

On the beginning, I had just the first part, but then I've shown this code to some experienced guy who works as a programmmer. By the time I realized that change he made, he has already been away.

You're talking about inconsistent use of paragraphs and brackets. Could you (or maybe someone else) point me out what exactly should I improve?

#26

October 25th, 2009, 08:05 PM

jacus

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Do you have any idea why this program isn't working for x=3 or x=-3?

#27

October 26th, 2009, 04:02 AM

jwdonahue

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Quote:

Originally Posted by jacus

Do you have any idea why this program isn't working for x=3 or x=-3?

You might start by defining what "isn't working" means.

#28

October 31st, 2009, 06:07 PM

jacus

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When I run the program, enter 3, it returns 'Enter the value of x. It must be between -pi and pi'.

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