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If a=cosalpha+isinalpha , b=cosbeta+isin...

If `a=cosalpha+isinalpha , b=cosbeta+isinbeta , c=cosgamma+isingamma` and `b/c+c/a+a/b=1`, then `cos(beta-gamma)+cos(gamma-alpha)+cos(alpha-beta )`=

A

a) `3/2`

B

b) `-3/2`

C

c) `0`

D

d) `1`

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