Guild Wars 2

Do they stack additively or multiplicatively?

~12% Berserkers power, adrenaline
10% Slasing power, with greatsword
10% Attack of opportunity, on bleeding target

What would you get if say you had slashing power and attack of opportunity?

Pretty sure it’s multiplicatively, or at least thats what i see with sturdy axes(berserker trait + 2 sigils of force gave me x1.12×1.05×1.05 amount and not x1.22)
And that’s awesome.