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Trignometry

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Joined:	9 Oct 2007
Post:	73

9 Oct 2007 01:19:53 IST

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519

MUltiple choice question........Rates asuured

None

IF cos 2

- cos

= sin 4

- sin

and tan

is not equal to 1,

THen cos3

- sin 3

equals

options........

1) 1

2) 2

3)3

4) none of these

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Comments (4)

Anshuman Bhujabal

Hot goIITian

Joined: 18 Aug 2007

Posts: 123

9 Oct 2007 06:18:31 IST

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It's a good question but it can be solved easily....
Here I don't know how to write theta , so I am using @ for theta

cos2@-cos@=sin4@-sin@
-2 sin(3@/2) sin(@/2) = 2 cos(5@/2) sin(3@/2)
sin(3@/2) { cos(5@/2) + sin(@/2) } =0
Hence sin(3@/2)=0
So sin3@=0 and cos3@=1-(2x0) = 1
Hence the answer is 1
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viswesh Nrayanan

Cool goIITian

Joined: 9 Oct 2007

Posts: 73

9 Oct 2007 10:49:45 IST

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Dude............ it has many solutions.........

urs is correct i guess..............

karthiksrichandra

New kid on the Block

Joined: 8 Jun 2007

Posts: 22

10 Oct 2007 21:40:56 IST

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cos2

-cos

=sin4

-sin@
-2 sin(3

/2) sin(

/2) = 2 cos(5

/2) sin(3

/2)
sin(3

/2) { cos(5

/2) + sin(

/2) } =0
Hence sin(3

/2)=0

=0 and

=30

srinivas meyy

New kid on the Block

Joined: 22 Aug 2007

Posts: 12

15 Oct 2007 02:16:42 IST

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hey is the ans 1

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