通过API文档查询Math类的方法，打印如下所示的近似圆，只要给定不同半径，圆的大小随之发生改变（如果需要使用复杂的数学运算，可以查阅Math类的方法或者参考9.3节的内容）-Through the API documentation inquiries Math class methods, print as follows Approximate round, as long as give different radius, round the size of subsequent changes (if necessary the use of complex mathematical calculations, you can access Math class method or reference to the 9.3 content)