Question

在△ABC中,AB=AC,AD⊥BC于点D,若△ABC\△ABD的周长分别为20cm和16cm,求AD的长

Answer 1

∵AB＝AC,AD⊥BC

∴BD＝CD

∴C△ABD＝C△ACD

∴C△ABD＋C△ACD＝2C△ABD＝32㎝

又∵C△ABD＋C△ACD＝AB＋BD＋AD＋AC＋CD＋AD＝AB＋AC＋BC＋2AD＝C△ABC＋2AD

∴AD＝0.5(C△ABD＋C△ACD－C△ABC)＝6㎝