解(2cosx-sinx)/(2cosx+sinx)
=[(2cosx-sinx)/cosx]/[(2cosx+sinx)/cosx]
=[2-sinx/cosx]/[2+sinx/cosx]
=(2-tanx）/(2+tanx)
=(2-1/2）/(2+1/2)
=(3/2)/(5/2)
=3/5