(1)以D为圆心,a为半经,画弧交AB于F,作角FDC平分线交BC于E.(2)AD/AB=d/a若DF平分角ADC,CFB=67.5度,∠EFC=∠FCE=22.5度,∠EFB=45度,BE=BF=a-d,BE/BC=(a-d)/a
