因为AB=AC,∠A=36°所以∠B=∠ACB=72°,又CD为∠ACB的平分线,所以∠DCB=∠ACD=∠ACB/2=36°,所以AD=CD=BC所以△ABC∽△CBD,所以AB/BC=BC/BD,即BC^2=AB*BD,将BC=CD=√5-1代人,得,（√5-1）^2=AB*BD=(AD+BD)*BD=(√5-1...