\(A=\left\{x: \frac{\pi}{6} \leq x \leq \frac{\pi}{3}\right\}\) అని మరియు f : A → R అనేది f(x) = cos x - x(1 + x) గా ఇవ్వబడితే, f(A) విలువ ఎంత?
1
[π/6, π/3]
2
[-π/3, -π/6]
3
\(\left[\frac{1}{2}-\frac{\pi}{3}\left(1+\frac{\pi}{3}\right), \frac{\sqrt{3}}{2}-\frac{\pi}{6}\left(1+\frac{\pi}{6}\right)\right]\)
4
\(\left[\frac{1}{2}+\frac{\pi}{3}\left(1-\frac{\pi}{3}\right), \frac{\sqrt{3}}{2}+\frac{\pi}{6}\left(1-\frac{\pi}{6}\right)\right] \)