1. 求下列三角函数的值(精确到 0.0001):
(1) $\sin 60^{\circ}$. (2) $\cos 52^{\circ} 18^{\prime}$. (3) $\tan 36^{\circ} 8^{\prime} 12^{\prime \prime}$.

1. (1) 0.866 0 (2) 0.611 5 (3) 0.730 2

(1) $\sin 60^{\circ}=\frac{\sqrt{3}}{2}\approx0.8660$
(2) $\cos 52^{\circ} 18^{\prime}\approx0.6115$
(3) $\tan 36^{\circ} 8^{\prime} 12^{\prime \prime}\approx0.7302$

2. 求下列各式的值(精确到 0.01):
(1) $\sin 25^{\circ}-2 \cos 35^{\circ}+\tan 72^{\circ}$. (2) $\cos 56^{\circ}-\sin 34^{\circ}+\tan 56^{\circ}$.

2. (1) 1.86 (2) 1.48

(1) $\sin 25^{\circ}-2 \cos 35^{\circ}+\tan 72^{\circ}\approx0.4226 - 2×0.8192 + 3.0777\approx1.86$
(2) $\cos 56^{\circ}-\sin 34^{\circ}+\tan 56^{\circ}\approx0.5592 - 0.5592 + 1.4826\approx1.48$

3. (1) 先用计算器求下列正弦值(精确到 0.0001),然后用“＜”把它们连接起来. $\sin 8^{\circ}, \sin 55^{\circ} 7^{\prime}, \sin 89^{\circ} 13^{\prime}, \sin 22^{\circ} 43^{\prime} 20^{\prime \prime}$.
(2) 先用计算器求下列余弦值(精确到 0.0001),然后用“＜”把它们连接起来.
$\cos 10^{\circ}, \cos 78^{\circ} 40^{\prime}, \cos 45^{\circ}, \cos 40^{\circ} 8^{\prime} 54^{\prime \prime}$.
(3) 由(1),(2)你能得到什么结论?

3. (1) $\sin 8^{\circ}=0.1392$，$\sin 55^{\circ}7'=0.8203$，$\sin 89^{\circ}13'=0.9999$，$\sin 22^{\circ}43'20''=0.3863$。$\sin 8^{\circ}＜\sin 22^{\circ}43'20''＜\sin 55^{\circ}7'＜\sin 89^{\circ}13'$
(2) $\cos 10^{\circ}=0.9848$，$\cos 78^{\circ}40'=0.1965$，$\cos 45^{\circ}=0.7071$，$\cos 40^{\circ}8'54''=0.7644$。$\cos 78^{\circ}40'＜\cos 45^{\circ}＜\cos 40^{\circ}8'54''＜\cos 10^{\circ}$
(3) 锐角的正弦值随角度的增大而增大，锐角的余弦值随角度的增大而减小