Which of the following is the condition for four points A,B,C,DA, B, C, DA,B,C,D to be concyclic?
AB⋅CD=BC⋅DAAB \cdot CD = BC \cdot DAAB⋅CD=BC⋅DA
PA⋅PC=PB⋅PDPA \cdot PC = PB \cdot PDPA⋅PC=PB⋅PD for some PPP
∠ABC+∠ADC=90∘\angle ABC + \angle ADC = 90^\circ∠ABC+∠ADC=90∘
All sides are equal