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x = cos 55^(@), y = cos 65^(@), z= cos 1...

`x = cos 55^(@), y = cos 65^(@), z= cos 175^(@) " then " xy+yz+ zx=`

A

`-3//4`

B

`3//4`

C

`1//2`

D

`3//2 `

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The correct Answer is:
A
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