Title Text:If you ever see someone using a capital xi in an equation, just observe them quietly to learn as much as you can before they return to their home planet. Origin:https://xkcd.com/2586/ https://www.explainxkcd.com/wiki/index.php/2586:_Greek_Letters 希腊字母 如果您曾经看到有人在方程式中使用大写字母xi，请安静地观察他们，在他们返回母星前了解他们，越多越好。 http://xkcd.in/comic?lg=cn&id=2586 数学使用大量希腊字母，通常一致地使用相同的字母来表示特定的常数或变… Read more