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Find The Value Of : sin(pi/18)*sin((5pi...

Find The Value Of :
`sin(pi/18)*sin((5pi)/18)*sin((7pi)/18)`

A

`1`

B

`1/8`

C

`1/4`

D

`1/2`

Text Solution

Verified by Experts

The correct Answer is:
B
We have,
`sin""(pi)/(18)sin""(5pi)/(18)sin""(7pi)/(18)`
`=cos""(8pi)/(18)sin""(5pi)/(18)sin""(7pi)/(18)`
`=cos""(pi)/(9)cos""(2pi)/(9)cos""(4pi)/(9)=(sin(2^(3)xx(n)/(9)))/(2^(3)sin""(pi)/(9))=1/8`
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OBJECTIVE RD SHARMA-TRIGONOMETRIC RATIOS AND IDENTITIES-Section I - Solved Mcqs
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