From Gogeometry Using : Additional points Tangents to a circle •(1) AF=ra=r+EB+BF=r+a2 •(2) AG=ra=r+DC+CG=r+a1 •(1-2) a1=a2 •(1+2) ra=r+a1=r+a2 => a1=a2=ra-r •Define X as the intersection of BC and circle ra •Define Y as the intersection of BC and circle r •CD and CY tangents to circle r => CD=CY •BE […]