The vector field F=⟨P,Q⟩\mathbf{F} = \langle P, Q \rangleF=⟨P,Q⟩ is irrotational. Which equation holds?
∂P∂y=∂Q∂x\frac{\partial P}{\partial y} = \frac{\partial Q}{\partial x}∂y∂P=∂x∂Q
∂P∂x=∂Q∂y\frac{\partial P}{\partial x} = \frac{\partial Q}{\partial y}∂x∂P=∂y∂Q
∂P∂x+∂Q∂y=0\frac{\partial P}{\partial x} + \frac{\partial Q}{\partial y} = 0∂x∂P+∂y∂Q=0
∂P∂y+∂Q∂x=0\frac{\partial P}{\partial y} + \frac{\partial Q}{\partial x} = 0∂y∂P+∂x∂Q=0