Trigonometric equations and inequalities

1003085701

Level: 
A
Find all \( x \), \( x\in\mathbb{R} \), such that \( \mathrm{cotg}^2x = - \mathrm{cotg}\,x \).
\( x\in\bigcup\limits_{k\in\mathbb{Z}}\left[ \left\{\frac{3\pi}4+k\pi \right\}\cup\left\{\frac{\pi}2+k\pi \right\} \right] \)
\( x\in\bigcup\limits_{k\in\mathbb{Z}}\left\{\frac{3\pi}4+2k\pi \right\} \)
\( x\in\bigcup\limits_{k\in\mathbb{Z}}\left\{\frac{3\pi}4+k\pi \right\} \)
\( x\in\bigcup\limits_{k\in\mathbb{Z}}\left\{\frac{\pi}2+k\pi \right\} \)

1003085702

Level: 
A
Solve \( 2\sin^2x = \sqrt2 \sin x \) for \( x \), where \( x\in\mathbb{R} \).
\( x\in\bigcup\limits_{k\in\mathbb{Z}}\left[ \{k\pi\}\cup\left\{ \frac{\pi}4+2k\pi \right\}\cup\left\{ \frac{3\pi}4+2k\pi\right\} \right] \)
\( x\in\bigcup\limits_{k\in\mathbb{Z}}\left[ \left\{ \frac{\pi}4+2k\pi \right\}\cup\left\{ \frac{3\pi}4+2k\pi\right\} \right] \)
\( x\in\bigcup\limits_{k\in\mathbb{Z}}\left[ \left\{ \frac{\pi}4+k\pi \right\}\cup\left\{ \frac{3\pi}4+k\pi\right\} \right] \)
\( x\in\bigcup\limits_{k\in\mathbb{Z}}\left[ \{2k\pi\}\cup\left\{ \frac{\pi}4+k\pi \right\}\cup\left\{ \frac{3\pi}4+k\pi\right\} \right] \)

1003085704

Level: 
A
The solution set of the equation \( \cos\!\left(2x - \frac{\pi}3 \right) = - 0.5 \), where \( 0 < x < 2\pi \), is:
\( \left\{ \frac{\pi}2; \frac{3\pi}2; \frac{5\pi}6; \frac{11\pi}6 \right\} \)
\( \left\{ \frac{\pi}2; \frac{3\pi}2 \right\} \)
\( \left\{ \frac{5\pi}6; \frac{11\pi}6 \right\} \)
\( \left\{ \frac{3\pi}2; \frac{5\pi}6; \frac{11\pi}6; \pi \right\} \)

1003085705

Level: 
A
Solving the equation \( 2\sin\!\left(x + \frac{\pi}4 \right) = \sqrt3 \) for \( x \), where \( x\in (0; \pi) \), you get:
\( x\in\left\{ \frac{\pi}{12};\frac{5\pi}{12} \right\} \)
\( x\in\left\{ \frac{\pi}{12} \right\} \)
\( x\in\left\{ \frac{3\pi}{12};\frac{5\pi}{12} \right\} \)
\( x\in\left\{ \frac{13\pi}{12};\frac{5\pi}{12} \right\} \)