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| Many students aren’t geting enough sleep at night, which means they end up feeling sleepy during class. | 1． |
| Taking a nap (午睡) during the day maybe a good way. | 2． |
| According to Forbes, a mid-afternoon nap can made | 3． |
| you clear your mind, and help you study much well. But | 4． |
| what time should students sleep? “The right time | 5． |
| should be between 10 and 30 minute,” Peter Venn, | 6． |
| an sleep expert said. | 7． |
| Sleeping at a short time, such as five minutes | 8． |
| or so, is not help. That’s just not enough time to rest. | 9． |
| And if you sleep for too long, you may wake up feeling uncomfortable. | 10． |
同类型试题
y = sin x， x∈R， y∈[–1，1]，周期为2π，函数图像以 x = (π/2) + kπ 为对称轴
y = arcsin x， x∈[–1，1]， y∈[–π/2，π/2]
sin x = 0 ←→ arcsin x = 0
sin x = 1/2 ←→ arcsin x = π/6
sin x = √2/2 ←→ arcsin x = π/4
sin x = 1 ←→ arcsin x = π/2
y = sin x， x∈R， y∈[–1，1]，周期为2π，函数图像以 x = (π/2) + kπ 为对称轴
y = arcsin x， x∈[–1，1]， y∈[–π/2，π/2]
sin x = 0 ←→ arcsin x = 0
sin x = 1/2 ←→ arcsin x = π/6
sin x = √2/2 ←→ arcsin x = π/4
sin x = 1 ←→ arcsin x = π/2
