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For each question, choose the correct answer.
William Perkin William Perkin was born in London in 1838. As a child he had many hobbies, including model making and photography. But it was the _____________ of chemistry that really interested him. At the age of 15, he went to college to study it.While he was there, he was _____________to make a medicine from coal. This didn’t go well, but when he was working on the problem, he found a cheap _____________ to make the colour purple. At that _____________ it was very expensive to make clothes in different colours. William knew he could make a business out of his new colour. Helped by his father and brother, William _____________ his own factory to make the colour. It sold well, and soon purple clothes _____________ very popular in England and the rest of the world. |
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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
