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If sin2A=2sinA cosAand sin20^(@)=K, " th...

If `sin2A=2sinA cosAand sin20^(@)=K, " then the value of " cos20^(@)cos80^(@)cos160^(@)`=__________.

A

K

B

`-sqrt(1-k^(2)`

C

`sqrt(1-k^(2))/(8)`

D

`-sqrt(1-k^(2))/(8)`

Text Solution

Verified by Experts

The correct Answer is:
B
(i) Multiply and divide the given expression with `sin20^(@)`
(ii) Use `sin^(2) A = 2sinA cosA`.
`sin(180-A) = sinA`.
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