If cosx+cosy+cosalpha=0 and sinx+siny+si...

If `cosx+cosy+cosalpha=0` and `sinx+siny+sinalpha=0` then `cot((x+y)/2)=`

A

`sin alpha`

B

`cos alpha`

C

`cot alpha`

D

`2 sin alpha`

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The correct Answer is:

B

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