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In some western countries, some people don't like the number 13 because they think 13 is an unlucky number. For example, they don't like to live on the thirteenth floor. One evening, Mr. Smith asked some friends to get t 1． . When all of his friends arrived, he asked them to sit at the table for d2．. He began to c3． the people. Suddenly, he cried out, "Oh, there are thirteen people here!" Everyone's face looked pale e 4． Mr. Brown. He said with a smile, "Don't won't, my friends. My wife will have a baby in a few weeks. So we have f 5． people here." All of the friends became happy again. "Congratulations!" they said to Mr. Brown. They all had a good time that evening.
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
