Given that \(q = 9i + 6j\) and \(r = 4i - 6j\), which of the following statements is true?

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.

waec 2011 furthermathematics

The correct answer is B. r and q are perpendicular

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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