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If sin(B+C-A),sin(C+A-B) and sin(A+B-C)are in A.P.; then cot A,cot B,cot C are in -

(a) GP

(b) HP

(c) AP

(d) None of these.

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,606

M says b. I haven't gotten to the solution analytically yet, though.

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
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Hi;

May I see what you did with M to get that?

**In mathematics, you don't understand things. You just get used to them.**

**I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.**

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
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Sure!

```
FullSimplify[Sin[b + c - a] + Sin[a + b - c] == 2 Sin[a + c - b]]
2 Cos[a] Cos[c] Sin[b] == Cos[b] Sin[a + c]
```

*Last edited by anonimnystefy (2014-07-14 05:02:14)*

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Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
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I do not understand it.

**In mathematics, you don't understand things. You just get used to them.**

**I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.**

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
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What do you not understand? I just rearranged the result a bit and got the answer.

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 88,882

They are in AP?

**In mathematics, you don't understand things. You just get used to them.**

**I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.**

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,606

The cot's are in HP.

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
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How are you representing the sines in AP is what I meant?

**In mathematics, you don't understand things. You just get used to them.**

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
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The same as Nehushtan did.

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
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Okay, I see what you saying.

**In mathematics, you don't understand things. You just get used to them.**

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
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Now to do it by hand...

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**bobbym****Administrator**- From: Bumpkinland
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You have the result, now you just have to back engineer the how.

**In mathematics, you don't understand things. You just get used to them.**

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**anonimnystefy****Real Member**- From: The Foundation
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I think I figured it out. I will post it when I write it out.

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**anonimnystefy****Real Member**- From: The Foundation
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Here's the solution.

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**bobbym****Administrator**- From: Bumpkinland
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Hi;

Got to get off, will look at it when I get back. You did good.

**In mathematics, you don't understand things. You just get used to them.**

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**gAr****Member**- Registered: 2011-01-09
- Posts: 3,479

Expanding gives:

hence in H.P.

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,606

Hi bobbym

See you later!

Thanks.

*Last edited by anonimnystefy (2014-07-14 06:29:01)*

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