theorem :: CONVEX3:3

for V being RealLinearSpace
for v1, v2, v3 being VECTOR of V st v1 <> v2 & v1 <> v3 & v2 <> v3 holds
ex L being Convex_Combination of V st
for A being non empty Subset of V st {v1,v2,v3} c= A holds
L is Convex_Combination of A