A_____________C______D_______________B∵点C.D分别为线段AB的两个黄金分割点∴AC:BC=BC:AB=BD:AD=AD:AB=(√5-1)/2∴AC=BD=(√5-1)/2BC=[(√5-1)/2]²AB=（3-√5)/2*AB∴CD=AB-2AC=AB-(3-√5）AB=6(√5-2)AB=6...