Express \(r = (12, 210°)\) in the form \(a i + b j\).
FURTHER MATHEMATICS
WAEC 2008
Express \(r = (12, 210°)\) in the form \(a i + b j\).
- A. \(6(-i + \sqrt{3} j)\)
- B. \(6(-\sqrt{3} i - j)\)
- C. \(6(i - \sqrt{3} j)\)
- D. \(6(i + \sqrt{3} j)\)
Correct Answer: B. \(6(-\sqrt{3} i - j)\)
Explanation
\(F = F \cos \theta i + F \sin \theta j\)
\(r = (12, 210°) = 12 \cos 210 i + 12 \sin 210 j\)
= \(- 6\sqrt{3} i - 6j\)
= \(6(-\sqrt{3} i - j)\)
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