Z = X + Y OR Z = X - Y
      _________
ΔZ = √ΔX² + ΔY²


Z = X * Y OR Z = X / Y
       __________________
_ΔZ_ = / ⎛_ΔX_⎞² + ⎛_ΔY_⎞²
  Z   √  ⎝  X ⎠    ⎝  Y ⎠


Z = Xⁿ

ΔZ = n X⁽ⁿ⁻¹⁾ ΔX, i.e. _ΔZ_ = n _ΔX_
                        Z        X


Z = 𝑓(X,Y,...)

ΔZ² = ⎛_∂f(X,Y)_ ΔX⎞² +  ⎛_∂f(X,Y)_ ΔY⎞² + ... 
      ⎝   ∂X       ⎠     ⎝   ∂Y       ⎠