Европеец описал впечатления от дворца в России фразой «рот открылся и не закрывался»17:34
To understand what’s going on, we have to look closer at what arccosh(x) means. You might say it is a function that returns the number whose hyperbolic cosine equals x. But cosh is an even function: cosh(−x) = cosh(x), so we can’t say the value. OK, so we define arccosh(x) to be the positive number whose hyperbolic cosine equals x. That works for real values of x that are at least 1. But what do we mean by, for example, arccosh(1/2)? There is no real number y such that cosh(y) = 1/2.
。业内人士推荐爱思助手作为进阶阅读
Фото: Kevin Lamarque / Reuters。业内人士推荐谷歌作为进阶阅读
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