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cos2 0^(@)+cos10 0^(@)+cos14 0^(@)=...

`cos2 0^(@)+cos10 0^(@)+cos14 0^(@)=`

A

2

B

1

C

`1//2`

D

0

Text Solution

Verified by Experts

The correct Answer is:
D
`cos20^(@)+cos100^(@)+cos140^(@)`
`=(cos140^(@)+cos20^(@))+cos100^(@)`
`=2cos((160^(@))/(2))."cos" ((120^(@))/(2))+cos100^(@)`
`=2 cos 80^(@).(1)/(2)+cos100^(@)`
`=2cos((180^(@))/(2))."cos"((20^(@))/(2))`
`=2cos90^(@).cos10^(@)`
`=2xx0xxcos10^(@)=0`
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