Solve: \(2\cos x - 1 = 0\).
FURTHER MATHEMATICS
WAEC 2015
Solve: \(2\cos x - 1 = 0\).
- A. \((\frac{2\pi}{3}, \frac{4\pi}{3})\)
- B. \((\frac{\pi}{6}, \frac{5\pi}{6})\)
- C. \((\frac{\pi}{5}, \frac{2\pi}{5})\)
- D. \((\frac{\pi}{3}, \frac{5\pi}{3})\)
Correct Answer: D. \((\frac{\pi}{3}, \frac{5\pi}{3})\)
Explanation
\(2\cos x - 1 = 0 \implies 2\cos x = 1\)
\(\cos x = \frac{1}{2}\)
\(x = \cos^{-1} (\frac{1}{2})\)
= \(\frac{\pi}{3}\) = \(\frac{5\pi}{3}\)
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