2個向量之間的度數？

我已選擇2個矢量，它們的本色應爲90°。

我試了cos，cos^-1，沒有cos calcualtion。但我的代碼的輸出爲：
0（無COS計算）
1（餘弦）
1.5707963267949（餘弦^ -1（ACOS））

local square = math.sqrt; 
local weaponVector, hitVector = , {x = 0, y = 0, z = 1,}, {x = 0, y = 1, z = 0,}; 
local xW, yW, zW = weaponVector.x, weaponVector.y, weaponVector.z; 
local xH, yH, zH = hitVector.x, hitVector.y, hitVector.z; 
local angleBetweenWeaponAndHitDirection = math.acos(math.abs(xW*xH+yW*yH+zW*zH) 
      /(square(xW*xW+yW*yW+zW*zW) * square(xH*xH+yH*yH+zH*zH))); 
if (angleBetweenWeaponAndHitDirection>180) then 
    angleBetweenWeaponAndHitDirection = 360-angleBetweenWeaponAndHitDirection; 
end 
print(angleBetweenWeaponAndHitDirection) 
print(math.cos(angleBetweenWeaponAndHitDirection)) 
print(math.acos(angleBetweenWeaponAndHitDirection))

來源

2011-08-17 lua