说明：  cordic算法的c语言实现，输入x，y两点坐标，自动计算得出改点与平面坐标轴（x轴正向）夹角，适用于整个坐标平面。于环境vc 6.0下编译通过。
(CORDIC algorithm realize the C language, input x, y coordinates of two points, are automatically calculated to change point and plane coordinate axis ( x axis positive ) angle, apply to the whole coordinate plane. In the environment of VC 6 under the compiler through.)