:OH2=OA2−AH2=R2−AB24=R2−CD24=R2−DK2=OD2−DK2=OK2=>OH=OKOH2=OA2−AH2=R2−AB24=R2−CD24=R2−DK2=OD2−DK2=OK2=>OH=OK
Xét 2 tam giác vuông OHE và OKE có :OH=OK, OE chung
=>ΔOHE=ΔOKE=>HE=KE=>ΔOHE=ΔOKE=>HE=KE
Do HE=KE =>HE+AB2=KE+CD2=>HE+AH=KE+CK=>AE=CE=>HE+AB2=KE+CD2=>HE+AH=KE+CK=>AE=CE(ĐPCM)