As shown in the figure, in the quadrilateral ABCD, ab = ad, CB = CD, point P is the point on AC, PE ⊥ BC is in E, PF ⊥ CD is in F, proving: PE = PF

As shown in the figure, in the quadrilateral ABCD, ab = ad, CB = CD, point P is the point on AC, PE ⊥ BC is in E, PF ⊥ CD is in F, proving: PE = PF

It is proved that in △ ABC and △ ADC, ab = adcb = CDAC = AC, ≌ ABC ≌ ADC (SSS), ≌ BCA = DCA, ≁ PE ⊥ BC in E, PF ⊥ CD in F, ≌ PE = PF