Đáp án:
Giải thích các bước giải:
\[\begin{array}{l}
a.0 \le |\sin x| \le 1 = > 1 \le y \le 3 = > \min y = 1 \Leftrightarrow x = \frac{\pi }{2} + k\pi ;\max y = 3 \Leftrightarrow x = k\pi \\
b.y = \cos x + \cos (x - \frac{\pi }{3}) = 2\cos (x - \frac{\pi }{6}).\cos \frac{\pi }{6} = \sqrt 3 \cos (x - \frac{\pi }{6})\\
- 1 \le \cos (x - \frac{\pi }{6}) \le 1 = > - \sqrt 3 \le y \le \sqrt 3 = > \min y = - \sqrt 3 \Leftrightarrow x = \frac{{7\pi }}{6} + k2\pi ;\max y = \sqrt 3 \Leftrightarrow x = \frac{\pi }{6} + k2\pi \\
c.y = 2 - \sqrt {\cos x} \\
dk:\cos x \ge 0\\
0 \le \cos x \le 1 = > 1 \le y \le 2 = > \min y = 1 \Leftrightarrow x = k2\pi ;\max y = 2 \Leftrightarrow x = \frac{\pi }{2} + k2\pi \\
d.y = \sin 2x + 1\\
- 1 \le \sin 2x \le 1 = > 0 \le y \le 2 = > \min y = 0;\max y = 2\\
e.y = \cos (x - \frac{\pi }{6})\\
- 1 \le \cos (x - \frac{\pi }{6}) \le 1 = > \min y = - 1;\max y = 1
\end{array}\]
