Упр.25.1 ГДЗ Мерзляк 10 класс Углубленный уровень (Алгебра)

1) cos(225В°); 2) sin(240В°);
3) cos(5ПЂ/4); 4) cos(-4ПЂ/3).

1. $$\cos 225^\circ=\cos(180^\circ+45^\circ)=-\cos 45^\circ=-\frac{\sqrt{2}}{2}$$
2. $$\sin 240^\circ=\sin(180^\circ+60^\circ)=-\sin 60^\circ=-\frac{\sqrt{3}}{2}$$
3. $$\cos \frac{5\pi}{4}=\cos\left(\pi+\frac{\pi}{4}\right)=-\cos \frac{\pi}{4}=-\frac{\sqrt{2}}{2}$$
4. $$\cos\left(-\frac{4\pi}{3}\right)=\cos\frac{4\pi}{3}=\cos\left(\pi+\frac{\pi}{3}\right)=-\cos\frac{\pi}{3}=-\frac{1}{2}$$

Ответ

$$-\frac{\sqrt{2}}{2};\ -\frac{\sqrt{3}}{2};\ -\frac{\sqrt{2}}{2};\ -\frac{1}{2}$$