ATAN2 returns the inverse trigonometric tangent, that is, the angle (in radians) between the x-axis and a line from point (NumberX, NumberY) to the origin.
ATAN2 返回 X 轴和从点 NumberX, NumberY 到原点的直线的夹角（用弧度表示）的反三角正切值。返回的角度在 -PI 和 PI 之间。