人 民 网 版 权 所 有 ，未 经 书 面 授 权 禁 止 使 用
P(all N points in some arc of length x)=N⋅xN−1P(\text{all } N \text{ points in some arc of length } x) = N \cdot x^{N-1}P(all N points in some arc of length x)=N⋅xN−1
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A put option is a contract that gives its owner the right to sell an asset at a future date at a predetermined price.
I don’t remember that.