如图,已知a,b,c三点在半径为2的圆o上,ob与ac相交于d,若∠acb=∠aoc,则(1/bd)-(1/bc)=

如图,已知a,b,c三点在半径为2的圆o上,ob与ac相交于d,若∠acb=∠aoc,则(1/bd)-(1/bc)=
如图,已知a,b,c三点在半径为2的圆o上,ob与ac相交于d,若∠acb=∠aoc,则(1/bd)-(1/bc)=

如图,已知a,b,c三点在半径为2的圆o上,ob与ac相交于d,若∠acb=∠aoc,则(1/bd)-(1/bc)=
∵∠acb=∠oac
∴ oa//bc
△AOD∽△CBD
bc/bd=oa/od
bc/bd-1=oa/od-1
(bc-bd)/bd=(oa-od)/od
=bd/od
=bc/oa
(bc-bd)/(bdxbc)=1/oa
=1/2
(1/bd)-(1/bc)=(bc-bd)/(bdxbc)
=1/2