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If vec a and vec b are unit vectors and ...

If `vec a` and `vec b` are unit vectors and `theta` is the angle between them, then `|vec a + vec b| =`

A

`2 (sin ) theta/2`

B

2 units

C

`2 cos theta`

D

`2 (cos) theta/2`

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The correct Answer is:
D
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