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10. vector algebra — Maths STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceMaths10. vector algebra1 Mark
MCQ
If $4i+j-k$ and $3i+mj+2k$ are at right angle, then $m = $
  • A
    $-6$
  • B
    $-8$
  • ✓
    $-10$
  • D
    $-12$
✓

Answer

Correct option: C.
$-10$
c
(c) Since angle between the vectors is ${90^o}$, therefore dot product of the vectors will be zero

or $(4i + j - k)\,.\,(3i + mj + 2k) = 0$

or $12 + m - 2 = 0$ or $m = - 10.$

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