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#26 2014-06-03 03:32:56
Re: Trig Proof Help
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'
I'm not crazy, my mother had me tested.
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#27 2014-06-03 05:00:54
- anonimnystefy
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- From: Harlan's World
- Registered: 2011-05-23
- Posts: 16,049
Re: Trig Proof Help
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)
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
The knowledge of some things as a function of age is a delta function.
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#28 2014-06-03 06:41:26
- gAr
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Re: Trig Proof Help
"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?
"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."
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#29 2014-06-12 19:16:36
Re: Trig Proof Help
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'
I'm not crazy, my mother had me tested.
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#30 2014-06-12 19:41:23
- Bob
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- Registered: 2010-06-20
- Posts: 10,624
Re: Trig Proof Help
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 (2014-06-12 19:44:27)
Children are not defined by school ...........The Fonz
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you! …………….Bob
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#31 2014-06-12 19:43:17
Re: Trig Proof Help
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'
I'm not crazy, my mother had me tested.
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#32 2014-06-12 19:45:15
- Bob
- Administrator
- Registered: 2010-06-20
- Posts: 10,624
Re: Trig Proof Help
Bob
Children are not defined by school ...........The Fonz
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you! …………….Bob
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#33 2014-06-12 21:52:31
- Bob
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- Registered: 2010-06-20
- Posts: 10,624
Re: Trig Proof Help
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
Children are not defined by school ...........The Fonz
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you! …………….Bob
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#34 2014-06-12 23:38:17
Re: Trig Proof Help
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)
'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'
I'm not crazy, my mother had me tested.
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#35 2014-06-13 00:42:27
- Bob
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- Registered: 2010-06-20
- Posts: 10,624
Re: Trig Proof Help
Tedious maybe, but good for you anyway.
I've ended up with cos(2A)
Bob
Children are not defined by school ...........The Fonz
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you! …………….Bob
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#36 2014-06-13 03:02:44
- ShivamS
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- Registered: 2011-02-07
- Posts: 3,648
Re: Trig Proof Help
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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#37 2014-06-13 05:40:44
Re: Trig Proof Help
I am sorry, things are not cancelling.
'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'
I'm not crazy, my mother had me tested.
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#38 2014-06-13 05:52:38
- ShivamS
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- Registered: 2011-02-07
- Posts: 3,648
Re: Trig Proof Help
Use a CAS to multiply it out.
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#39 2014-06-13 05:55:37
Re: Trig Proof Help
There will be no CAS when I will show this to Amrita
'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'
I'm not crazy, my mother had me tested.
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#40 2014-06-13 06:09:28
- bobbym
- bumpkin
- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606
Re: Trig Proof Help
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.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.
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#41 2014-06-13 06:09:42
- ShivamS
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- Registered: 2011-02-07
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Re: Trig Proof Help
Then you will have to multiply by hand - error prone.
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#42 2014-06-13 07:43:57
- Bob
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Re: Trig Proof Help
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
Children are not defined by school ...........The Fonz
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you! …………….Bob
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#43 2014-06-13 07:52:49
- ShivamS
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- Registered: 2011-02-07
- Posts: 3,648
Re: Trig Proof Help
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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#44 2014-06-13 08:00:43
- Bob
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- Registered: 2010-06-20
- Posts: 10,624
Re: Trig Proof Help
But it's good for the brain.
Bob
Children are not defined by school ...........The Fonz
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you! …………….Bob
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