Find the value of the constant k for which \(a = 4 i - k
FURTHER MATHEMATICS
WAEC 2008
Find the value of the constant k for which \(a = 4 i - k j\) and \(b = 3 i + 8 j\) are perpendicular.
- A. \(\frac{2}{3}\)
- B. 2
- C. 3
- D. \(\frac{3}{2}\)
Correct Answer: D. \(\frac{3}{2}\)
Explanation
For perpendicular vectors, their dot product = 0.
\((4i - kj). (3i + 8j) = 12 - 8k = 0\)
\(8k = 12 \implies k = \frac{3}{2}\)
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