在RT△ACD中:∵AD=a,AC=√ab,∴CD=√(ab-a²).
在Rt△ABC中:∴BC=b,AC=√ab,∴AB=√(b²-ab),
∵AC/BC=√ab/b,
AD/AC=a/√ab=√ab/b,
CD/AB=√(ab-a²)/√(b²-ab)=√a(b-a)/√b(b-a)=√ab/b,
∴△ADC∽△CAB.
∴∠ACD=∠ACB,
∴AD‖BC,即CD⊥BC.
在RT△ACD中:∵AD=a,AC=√ab,∴CD=√(ab-a²).
在Rt△ABC中:∴BC=b,AC=√ab,∴AB=√(b²-ab),
∵AC/BC=√ab/b,
AD/AC=a/√ab=√ab/b,
CD/AB=√(ab-a²)/√(b²-ab)=√a(b-a)/√b(b-a)=√ab/b,
∴△ADC∽△CAB.
∴∠ACD=∠ACB,
∴AD‖BC,即CD⊥BC.