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if veca and vecb are unit vectors such ...

` if veca and vecb ` are unit vectors such that ` veca. vecb = cos theta` , then the value of `| veca + vecb|`, is

A

`2 sin theta//2`

B

` 2 sin theta`

C

` 2 cos theta //2`

D

` 2 cos theta `

Text Solution

Verified by Experts

The correct Answer is:
C
we have,
` |veca.vecb|^(2) + |vecb|^(2) + 2(veca.vecb)`
` Rightarrow |veca + vecb|^(2) = 1+1+2 cos theta = 4 cos^(2) theta/2`
` Rightarrow |veca +vecb| = 2 cos " " theta/2`
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