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Mathematics

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 Joined: 20 Feb 2012 Post: 12
26 Feb 2012 19:58:35 IST
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what is the value of sin36
CBSE Board , CBSE X , Mathematics

what is the value of sin36

Scorching goIITian

Joined: 20 Jul 2011
Posts: 256
28 Feb 2012 21:31:23 IST
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We know that cos2x = 1-2sin^2x

Let x = 18

then, cos 36 = 1-2sin^2(18)

= 1 - 2(root5 - 1)^2/4^2

= (root5 + 1)/4

and also, we know that

sin36 = root[ 1 - cos^2(36)]

Solving it further, you'll get sin36 = root[ 10 - 2root5] / 4

Scorching goIITian

Joined: 18 Apr 2012
Posts: 208
26 Jun 2012 12:38:15 IST
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The answer given by Sumiran agrawal is nice and I have come up with the exact answer but have some problem in posting the method but the answer is -0.991778853.

Scorching goIITian

Joined: 20 Jul 2011
Posts: 256
26 Jun 2012 20:25:55 IST
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How do you getting 0.99...

The answer to this is 0.587 (approx.).

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