从技术角度而言，正则表达式是表示某种模式的字符串(也就是说，由字母、数字和符号组成的字符序列)，用于定义零或更长的字符串。

Technically speaking, a regular expression is a string (that is, a sequence of characters composed of letters, Numbers, and symbols) that represents a pattern defining zero or more strings.

youdao

从现代数学的角度看来，它们都是符号。

From a modern mathematical point of view, they were all alike symbols.

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在从语言学角度向符号学的转换中，在后现代视觉文化领域，集合成为了一种被广泛运用的言说方式。

In the postmodern visual cultural field, and in its transference from linguistics to semiotics, assemblage becomes a widely used mode of utterance.

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I'm using the fact that when you take a cosine and change the angle inside the cosine, it doesn't care. whereas, if you go to the sine and change the angle inside the sine, it becomes minus sine.

我用了一个结论,当你使用余弦函数时,改变角度的正负,函数值不变,而对于正弦函数,改变角度的符号,则函数值也会变号

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