Proof: connect AO and extend BC to m, connect VM,
Because OA1/va, A 1 is on VM, OA1/va = om/am;
Similarly, connect BO, extend AC to N, and connect VN; Connect CO and extend AB to p, connect VP,
Then OB 1/VB = ON/BN, OC 1/VC = OP/CP,
In the triangle ABC, OM/AM = SBOC/SABC (because the bottom is BC).
Similarly ON/BN = SAOC/SABC, OP/CP = SAOB/SABC,
The result is OA1/va+ob1/VB+oc1/VC.
= OM/AM+ON/VN+OP/CP
= SBOC/ SABC +SAOC/ SABC +SAOB/ SABC
= (SBOC+SAOC+SAOB)/SABC
= SABC/SABC
= 1 is a fixed value.