如图,在Rt△ABC中,∠ACB=90°,CD⊥AB于D,设AC=b,BC=a,AB=c,CD=h. 求证:1/a2+1/b2=1/h2.
问题描述:
如图,在Rt△ABC中,∠ACB=90°,CD⊥AB于D,设AC=b,BC=a,AB=c,CD=h.
求证:
+1 a2
=1 b2
.1 h2
答
证明:在直角△ABC中,∠ACB=90°,CD⊥AB,则△ACB∽△ADC∽△CDB,
=CD AC
,即BD BC
=CD2 AC2
,BD2 BC2
∵h2(
+1 a2
)=1 b2
+CD2 BC2
=CD2 AC2
+CD2 BC2
BD2 BC2
=
=1,BC2 BC2
∴
+1 a2
=1 b2
.1 h2