Math.tan(Double d) : 求角度的Tan值
Double angle = 30
Double radians = angle *(Math.PI / 180)
Double result = Math.Tan(radians)
Math.atan(Double d): 根据值来求角度 radians = Math.Atan(result)
angle = radians *(180 / Math.PI)Math.atan2(y, x) ：依据坐标来求角度
