theorem :: CONVEX4:88
for V being ComplexLinearSpace
for v1, v2, v3 being VECTOR of V
for L being C_Linear_Combination of {v1,v2,v3} st v1 <> v2 & v2 <> v3 & v3 <> v1 & L is convex holds
( ex r1, r2, r3 being Real st
( r1 = L . v1 & r2 = L . v2 & r3 = L . v3 & (r1 + r2) + r3 = 1 & r1 >= 0 & r2 >= 0 & r3 >= 0 ) & Sum L = (((L . v1) * v1) + ((L . v2) * v2)) + ((L . v3) * v3) )