Given that \(q = 9i + 6j\) and \(r = 4i - 6j\), which of
FURTHER MATHEMATICS
WAEC 2011
Given that \(q = 9i + 6j\) and \(r = 4i - 6j\), which of the following statements is true?
- A. r and q are collinear
- B. r and q are perpendicular
- C. The magnitude of r is 52 units
- D. The projection of r on q is \(\sqrt{117}\) units.
Correct Answer: B. r and q are perpendicular
Explanation
The dot product of two perpendicular forces = 0
\((9i + 6j).(4i - 6j) = 36 - 36 = 0\)
Hence, r and q are perpendicular.
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