GeometricScene[{{A.,B.,C.,D.,O.,E.,F.,G.,H.},{}},{{CircleThrough[{A.},O.]},{B.∈CircleThrough[{A.},O.],C.∈CircleThrough[{A.},O.],D.∈CircleThrough[{A.},O.],GeometricAssertion[{Line[{A.,O.,C.}],Line[{B.,O.,D.}]},"Perpendicular"]},{GeometricAssertion[{Line[{E.,B.,F.}],CircleThrough[{A.},O.]},{"Tangent",B.}],GeometricAssertion[{Line[{F.,C.,G.}],CircleThrough[{A.},O.]},{"Tangent",C.}],GeometricAssertion[{Line[{H.,D.,G.}],CircleThrough[{A.},O.]},{"Tangent",D.}],GeometricAssertion[{Line[{E.,A.,H.}],CircleThrough[{A.},O.]},{"Tangent",A.}]}},{GeometricAssertion[{Polygon[{E.,F.,G.,H.}]},"Regular"]}]
