Math 方法的使用

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