Question

Допоможіть будь ласка з алгеброю дуже терміново

Answer 1

2.

$100^o$ - II чверть

$sin100^o > 0$

$210^o$- III чверть

$cos210^o < 0$

$\underline {sin100^o cos120^o < 0}$

3.

$1) cos\alpha\\sin^2\alpha+cos^2\alpha=1\\ \\\\0,8^2 +cos^2\alpha=1\\\\\\0,64+cos^2x=1\\ \\\\cos^2\alpha=1-0,64 \\ \\\\cos^2\alpha= 0,36 \\ \\\\cos\alpha=-\sqrt{0,36}\\\\cos\alpha=-0,6$

$2) tg\alpha\\tg\alpha=\frac{sin\alpha}{cos\alpha}\\ \\tg\alpha=\frac{0,8}{-0,6}\\ \\tg\alpha=- \frac{8 }{ 6 }\\\\\underline{tg\alpha=- \frac{ 4 }{ 3 }}$

4.

$sin 2x=-\frac{1}{2}\\\\sin 2x=-sin\frac{\pi}{6}=sin(-\frac{\pi}{6})\\\\2x=-\frac{\pi}{6}\pi+2n\pi\ \ \ |:2\ \ \ \ \ \ \ 2x=\frac{7}{6}\pi+2n\pi\ \ \ |:2\\\\\underline{x=-\frac{1}{12}\pi+n\pi\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ x=\frac{7}{12}\pi+n\pi}$