∵∠C=90°,DE⊥AB,AD平分∠CAB,∴CD=DE.又∵AD=AD,∴Rt△ACD≌Rt△AED(HL),∴AC=AE,∵AB=AC∴△ABC是等腰直角三角形∴AC=√2/2AB=√2/2×6=3√2∠B=45°∴△BDE是等腰直角三角形DE=BE=AB-AE=AB-AC=6-3√2∴BD=√2DE=√2(6-3√2)=6√2-6∴△BDE的周长=BD+DE+BE=6√2-6+6-3√2+6-3√2=6