664. Привести к углу α, где 0 ≤ α ≤ π/2: 1) cos 110°; 2) sin 148°; 3) sin (5π/4); 4) cos (4π/3); 5) tg 291°; 6) ctg 305°; 7) ctg (5π/3); 8) sin (5π/6); 9) cos (41π/6); 10) sin (15π/7); 11) tg (8π/3); 12) ctg (28π/5).

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Accepted Answer

\(\cos 110^\circ=-\cos 70^\circ\).
\(\sin 148^\circ=\sin 32^\circ\).
\(\sin\frac{5\pi}{4}=-\sin\frac{\pi}{4}\).
\(\cos\frac{4\pi}{3}=-\cos\frac{\pi}{3}\).
\(\operatorname{tg}291^\circ=-\operatorname{tg}69^\circ\).
\(\operatorname{ctg}305^\circ=-\operatorname{ctg}55^\circ\).
\(\operatorname{ctg}\frac{5\pi}{3}=-\operatorname{ctg}\frac{\pi}{3}\).
\(\sin\frac{5\pi}{6}=\sin\frac{\pi}{6}\).
\(\cos\frac{41\pi}{6}=\cos\frac{5\pi}{6}=-\cos\frac{\pi}{6}\), так как \(\frac{41\pi}{6}-6\pi=\frac{5\pi}{6}\).
\(\sin\frac{15\pi}{7}=\sin\left(2\pi+\frac{\pi}{7}\right)=\sin\frac{\pi}{7}\).
\(\operatorname{tg}\frac{8\pi}{3}=\operatorname{tg}\frac{2\pi}{3}=-\operatorname{tg}\frac{\pi}{3}\).
\(\operatorname{ctg}\frac{28\pi}{5}=\operatorname{ctg}\frac{3\pi}{5}=-\operatorname{ctg}\frac{2\pi}{5}\).

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