In Fig. 6.61, two chords AB and CD intersect each other at the point P. Prove that:

(i) Δ APC ~ Δ DPB


(ii) AP . PB = CP . DP



(i) In triangle APC and DPB,

CAP = BDP (Angles on the same side of a chord are equal)


APC = DPB (Opposite angles)


Hence,


Δ APC ~ Δ DPB (By AAA similarity)


(ii) Since, the two triangles are similar


Hence,



Or,


AP * PB = CP * DP


Hence, proved


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