In the figure, P is the centre of the circle. Two chords AB and CD are parallel to each other. Prove ∠CPA=∠DPB.
Consider ΔOPC and ΔOPD
Since, OP=OP as a common side.
∠POC=POD [Right angle]
PC=PD
Thus, ΔPOC≅ΔPOD from RHS Criterion
So, ∠OPC=∠OPD.....(i)
Similar way, we can prove ΔLPA≅ΔLPB
So, ∠LPA=∠LPB.....(ii)
From equation(ii)-equation(i), we get
⇒∠LPA−∠OPC=∠LPB−∠OPD
∴∠CPA=∠DPB