是一个计算圆周长，面积的程序，主要是先设定半径和原点。- Is a calculated circumference, area programs, primarily to set the radius and origin.

可以直接使用的跨域小插件。设置为Access-Control-Allow-Origin *即可轻松跨域(Cross domain small plug-ins that can be used directly. Setting it to Access-Control-Allow-Origin * can easily cross domains)