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#1 2014-01-28 16:15:21

niharika_kumar
Member
From: Numeraland
Registered: 2013-02-12
Posts: 1,028

trigonometry#3

the value of

options are:-
A) 4.5
B) 4
C) 8
D) 9


friendship is tan 90°.

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#2 2014-01-28 21:16:06

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,532

Re: trigonometry#3

hi Niharika,

Oh, that looks evil.  But what can you do?  Just use trig. formulas as they present themselves.

(i)  Write sec as 1/cos and cosec as 1/sin

(ii) Put over common denominator.

(iii) Throw in some 2s to make root 3 into sin(x) and 1 into cos(x) and to get an extra factor of 2 on the denominator.  Where you introduce a /2 or x2, compensate by x2 or /2 as necessary.  Leave any additional 2s alone.

(iv) Use sin(2y) = 2sin(y).cos(y) on the denominator and sin(x-y) = sin(x).cos(y) - sin(y).cos(x) on the numerator.

(v) Simplify.

(vi) Look smug when all that is left is the answer.  (What! no 'smug' smiley?  I'll just have to make do with these.) smile up

Bob


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

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#3 2014-01-30 04:49:43

niharika_kumar
Member
From: Numeraland
Registered: 2013-02-12
Posts: 1,028

Re: trigonometry#3

thank you bob.
I was breaking my head on this without getting the head or tail of the question.You made it so simple.
I got the answer and its right.
Thanks again. smile


friendship is tan 90°.

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#4 2014-01-30 04:52:23

Agnishom
Real Member
From: The Complex Plane
Registered: 2011-01-29
Posts: 18,884
Website

Re: trigonometry#3

Did you mean 20 degrees?


'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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#5 2014-01-30 04:56:05

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,655

Re: trigonometry#3

Yes, and it can also be done with Taylor series and interval arithmetic,


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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#6 2014-01-30 04:59:01

niharika_kumar
Member
From: Numeraland
Registered: 2013-02-12
Posts: 1,028

Re: trigonometry#3

taylor series and interval arithmetic...
Can you please explain something about that?


friendship is tan 90°.

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#7 2014-01-30 05:02:24

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,655

Re: trigonometry#3

It was for Agnishom actually. He now has the tools to answer questions like that. It exploits the weaknesses if the multiple choice question system. Your teacher will hate 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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#8 2014-01-30 06:07:31

Agnishom
Real Member
From: The Complex Plane
Registered: 2011-01-29
Posts: 18,884
Website

Re: trigonometry#3

What is the weakness? Interval system?


'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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#9 2014-01-30 06:13:27

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,655

Re: trigonometry#3

The multiple choice system is particularly suited to exploitation by the methods of experimental mathematics. You can look up Taylor series and interval arithmetic inside your package and please do so.

Mind you I recommend that you first understand the standard method like what Bob did. Once you do you can experiment with other methods.

Also, it is not a shortcut, it requires that you learn more mathematics. But in case you get stuck an alternative method is always good.


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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