fact: Definition Cd O E S U1 U2 P X Y := Cs O E S U1 U2 /\ Coplanar P S U1 U2 /\ (exists PX, Projp P PX S U1 /\ Cong_3 O E X S U1 PX) /\ (exists PY, Projp P PY S U2 /\ Cong_3 O E Y S U2 PY).
imports: GeoCoq.Axioms.tarski_axioms