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(i) If vec a, vec b and vec a + vec b ar...

(i) If `vec a, vec b` and `vec a + vec b` are unit vectors, then prove that the angle between `vec a` and `vec b` is `(2pi)/(3)`
(ii) If `(2 hat i + hat j - 3 hat k`) and `(m hat i + 3 hat j - hat k)` are perpendicular to each other , then find m.

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The correct Answer is:
(i) `|vec a|^(2) + 2 vec a . Vec b + |vec b^(2)| = 1`
(ii)`sqrt(266)` sq.unit
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