一个在控制台上画图的小程序，用c语言实现，可以画直线矩形圆圆弧等，用统一的数据结构-A drawing program on the console, using c language, can draw a straight line rectangle circular arc, with a unified data structure

通过梯形积分法，通过输入定义域，可求得固定方程的弧长-By trapezoidal integration, arc can be obtained by entering the domain with fixed equation