P and Q are points on sides CA and CB respectively of Δ ABC right angled at C. Prove that AQ2 + BP2 = AB2 + PQ2
In right- angled triangles ACQ and PCB, we have
AQ2 = AC2 + CQ2 and PB2 = PC2 + CB2
⇒AQ2 + BP2 = (AC2 + CQ2) + (PC2 + CB2)
⇒AQ2 + BP2 = (AC2 + BC2) + (PC2 + QC2)
⇒AQ2 + BP2 = AB2 + PQ2
AC2 + BC2 - AB2 and PC2 + QC2 - PQ2 [By Pythagoras theorem]