△ABC≌△abc,AD为高,ad为高,则Rt△ADB与Rt△adb,AB=ab,∠ABD=∠adb,根据(HL判定知)Rt△ADB≌Rt△adb,所以AD=ad,或者根据AD=AB Sin[∠ABD]=ab Sin[∠abd]=ad.其它高类似证明即可.角平分线AD,ad△ADB与△adb,AB=ab,∠...