How to detect if a part hits back of a player character?

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#1

I have a script for a sword and I want when the sword hits the player character, it will do more damage if it hits the back.

I have tried to use Vector3:Dot() but it did not work I may of did it incorrectly

local Tool = script.Parent
local Handle = Tool.Handle
local Anims = Tool.Anims
local plrowner = script:FindFirstAncestorWhichIsA("Player") --player holding the part
local RaycastHitbox = require(game.ServerScriptService.RaycastHitboxV4)
local Hitbox = RaycastHitbox.new(Tool.Hitbox)

local de = false
local canHit = false
local combo = 1

config = {
	Damage = 30,
	AttackTime = 0.05,
	Cooldown = .9
}

Hitbox.OnHit:Connect(function(hit, humanoid)
	if canHit == false then return end
	canHit = false
	if humanoid.Parent ~= script.Parent.Parent and humanoid.Parent.Parrying.Value == false then
		humanoid:TakeDamage(config.Damage)
		task.wait(.35)
	elseif humanoid.Parent.Parrying.Value == true then
		print("ouchies")
		plrowner.Character.Vulnerable.Value = true
		plrowner.Character.HumanoidRootPart.Anchored = true
		plrowner.Character.Star.Star.Transparency = 0
		wait(2)
		plrowner.Character.Vulnerable.Value = false
		plrowner.Character.HumanoidRootPart.Anchored = false
		plrowner.Character.Star.Star.Transparency = 1
	end
	canHit = true
end)
script.Parent.Hit1.OnServerEvent:Connect(function(Player)
	if de == false then
		de = true
		local Humanoid = Player.Character.Humanoid
		local AnimationsList = Anims:GetChildren()
		local load = Humanoid:LoadAnimation(Anims.Slice1)
		load:Play()
		Player.Character.Attacking.Value = true
		Tool.Hitbox["sword slash 1"]:Play()
		Hitbox:HitStart()
		Tool.blade.Trail.Enabled = true
		wait(config.AttackTime)
		canHit = true
		Humanoid.WalkSpeed = 1
		wait(config.Cooldown)
		Player.Character.Attacking.Value = false
		Tool.blade.Trail.Enabled = false
		Humanoid.WalkSpeed = 12
		Hitbox:HitStop()
		canHit = false
		de = false
	end
end)

script.Parent.Hit2.OnServerEvent:Connect(function(Player)
	if de == false then
		de = true
		local Humanoid = Player.Character.Humanoid
		local AnimationsList = Anims:GetChildren()
		local load = Humanoid:LoadAnimation(Anims.Slice2)
		wait(config.AttackTime)
		load:Play()
		Player.Character.Attacking.Value = true
		Tool.blade.Trail.Enabled = true
		Tool.Hitbox["sword slash 2"]:Play()
		Hitbox:HitStart()
		canHit = true
		Humanoid.WalkSpeed = 1
		wait(config.Cooldown)
		Player.Character.Attacking.Value = false
		Tool.blade.Trail.Enabled = false
		Humanoid.WalkSpeed = 12
		Hitbox:HitStop()
		canHit = false
		de = false
	end
end)

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