Câu 1: A
ĐK: $x-1\ge 0\Leftrightarrow x\ge 1$
Câu 2: D
ĐK:
(1) $\tan x\ne 1\Leftrightarrow x\ne \dfrac{\pi}{4}+k\pi$
(2) $\cos x\ne 0\Leftrightarrow x\ne \dfrac{\pi}{2}+k\pi$
x phải thoả mãn cả (1) và (2).
Câu 3: C
ĐK: $1-x^2\ge 0\Leftrightarrow x^2\le 1\Leftrightarrow -1\le x\le 1$
Câu 4: D
ĐK: $\sin x\ne 0,5\Leftrightarrow x\ne \dfrac{\pi}{6}+k2\pi$, $x\ne \dfrac{5\pi}{6}+k2\pi$
Câu 5: A
$-2\le 2\cos x\le 2$
$\Leftrightarrow 1\le y\le 5$
$\to \min=1$, $\max=5$
Câu 6: D
$-5\le -5\sin x\le 5$
$\Leftrightarrow -2\le y\le 8$
$\to \min=-2; \max=8$
Câu 7: D
$\sin(2x-\dfrac{\pi}{6})=-1$
$\Leftrightarrow 2x-\dfrac{\pi}{6}=\dfrac{3\pi}{2}+k2\pi$
$\Leftrightarrow x=\dfrac{5\pi}{6}+k\pi$
hay $x=\dfrac{-\pi}{6}+k\pi$
