WAEC - Further Mathematics (2015 - No. 2)
Solve: \(2\cos x - 1 = 0\).
\((\frac{2\pi}{3}, \frac{4\pi}{3})\)
\((\frac{\pi}{6}, \frac{5\pi}{6})\)
\((\frac{\pi}{5}, \frac{2\pi}{5})\)
\((\frac{\pi}{3}, \frac{5\pi}{3})\)
설명
\(2\cos x - 1 = 0 \implies 2\cos x = 1\)
\(\cos x = \frac{1}{2}\)
\(x = \cos^{-1} (\frac{1}{2})\)
= \(\frac{\pi}{3}\) = \(\frac{5\pi}{3}\)