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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

`3/2`

D

`1/2`

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The correct Answer is:
A
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