中文说明：基于CORDIC算法计算反正切函数。输入横坐标纵坐标及迭代次数，输出角度及弧度值；附CORDIC英文文档说明
English Description：
The arctangent function is calculated based on CORDIC algorithm. Input the abscissa, ordinate and iteration times, output the angle and radian value, with CORDIC English document description