程序为对1.txt中的三点读取,并且对其进行求圆弧参数(包括圆心,半径,起始角,终角),最后在窗口中画出圆弧-Procedures for the three points 1.txt read, and their parameters for arc (including the center of a circle, radius, start angle, end angle), and finally in the window to draw arc