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Thanks.

Explain the second line please?

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'

'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'

'You have made another human being happy. There is no greater accomplishment.' -bobbym

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,796

Well, you get the middle term from the two middle terms of the previous line and the last term from the last term of the previous line.

*Last edited by anonimnystefy (2014-06-03 05:52:23)*

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**gAr****Member**- Registered: 2011-01-09
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"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense" - Buddha?

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Help me!

Evaluate

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'

'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'

'You have made another human being happy. There is no greater accomplishment.' -bobbym

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,654

hi Agnishom,

You'll need a large sheet of paper or to write small.

Once you've multiplied this out, nearly everything cancels.

I converted all to sines with

But you can also simplify with the double angles instead.

Bob

*Last edited by bob bundy (2014-06-12 19:44:27)*

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

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Regarding writing small:

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'

'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'

'You have made another human being happy. There is no greater accomplishment.' -bobbym

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,654

Bob

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,654

But .....

Thought I'd made a mistake as my final simplified answer was a trig function of A, not a number.

Couldn't find a mistake so I set up the expression in Excel and tried a few angles. I consistently got the result I'd got by algebra and trig formulas.

Bob

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

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What results are you getting?

That multiplication is tedious, I've not done it.(yet)

*Last edited by Agnishom (2014-06-12 23:38:37)*

'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'

'You have made another human being happy. There is no greater accomplishment.' -bobbym

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,654

Tedious maybe, but good for you anyway.

I've ended up with cos(2A)

Bob

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**ShivamS****Member**- Registered: 2011-02-07
- Posts: 3,638

Agnishom, it would have been much simpler if I have seen cos(2A+2B) at the end instead...

I am getting cos(2A).

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I am sorry, things are not cancelling.

'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'

'You have made another human being happy. There is no greater accomplishment.' -bobbym

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**ShivamS****Member**- Registered: 2011-02-07
- Posts: 3,638

Use a CAS to multiply it out.

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There will be no CAS when I will show this to Amrita

'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'

'You have made another human being happy. There is no greater accomplishment.' -bobbym

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 91,612

Hi Agnishom;

Just to show you it is possible

`TrigReduce[2 Sin[B]^2 + 4 (Cos[B] Cos[B] - Sin[A] Sin[B])*Sin[A] Sin[B] + (Cos[A]^2 - Sin[A]^2) (Cos[B]^2 - Sin[B]^2) - 2 Sin[A] Cos[B]*2 Sin[B] Cos[B]]`

**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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**ShivamS****Member**- Registered: 2011-02-07
- Posts: 3,638

Then you will have to multiply by hand - error prone.

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,654

It took me five lines on a sheet of A4 paper. Admittedly, the lines were quite long, but two long terms cancelled straight away, so that made it simpler. I'd show you but then you wouldn't get the benefit of doing it yourself .

Is this what the computer-wise generation has come to; that we cannot multiply out a simple expression ?

Go to it, boy wonder!

Bob

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**ShivamS****Member**- Registered: 2011-02-07
- Posts: 3,638

bob bundy wrote:

Is this what the computer-wise generation has come to; that we cannot multiply out a simple expression ?

Go to it, boy wonder!

Bob

We're lazy.

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**bob bundy****Moderator**- Registered: 2010-06-20
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But it's good for the brain.

Bob

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