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cos 20^@.cos 40^@.cos 60^@ cos 80^@=...

`cos 20^@.cos 40^@.cos 60^@ cos 80^@=`

A

`1//2`

B

`1//2^2`

C

`1//2^3`

D

`1//2^4`

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The correct Answer is:
D
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Prove that cos 20^@ cos 40^@ cos60^@ cos80^@=1/16

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Prove that cos 20^(@)cos40^(@)cos60^(@)cos80^(@)=(1)/(16)

Prove that :cos20^(@)cos40^(@)cos60^(@)cos80^(@)=(1)/(16)

Prove that cos20^(@)cos40^(@)cos60^(@)cos80^(@)=(1)/(16)

Prove that: cos20^(@)cos40^(@)cos60^(@)cos80^(@)=(1)/(16)

Prove that: i) cos10^(@)cos30^(@)cos50^(@)cos70^(@)=3/16 ii) cos20^(@)cos40^(@)cos60^(@)cos80^(@)=1/16 iii) 4cos12^(@)cos48^(@)cos72^(@)=cos36^(@) iv) cos40^(@) cos80^(@)cos160^(@)=-1/8

A=cos20^(@)cos40^(@)cos60^(@)cos80^(@),B=cos60cos42^(@)cos66^(@)cos78^(@) and C=cos36^(@)cos72^(@)cos108^(@)cos144^(@) then

Statement-1: The vlaue of cos20^(@)cos40^(@)cos60^(@)cos80^(@)is1/16. Statement-2: for any theta, cos thetacos(60^(@)-theta)cos(60^(@)+theta)=1/4cos3theta

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