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Let 'veca' and 'vecb' be two unit vector...

Let 'veca' and 'vecb' be two unit vectors and 'theta' is the angle between them. Then 'veca,+vecb' is a unit vector if

A

theta=pi/4'

B

theta=pi/3'

C

theta=pi/2'

D

theta=2 fra.pi/3'

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The correct Answer is:
D
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