如图,在△ABC中,点D在边AB上,满足且∠ACD=∠ABC,若AC=2,AD=1,求DB的长.
∵∠ACD=∠ABC,∠BAC=∠CAD,∴△ADC∽△ACB.∴.∵AC=2,AD=1,∴.∴DB=AB-AD=3.