theorem Th21: :: ENTROPY1:21

for p being non empty FinSequence of REAL
for q being FinSequence of REAL
for M being Matrix of REAL holds
( M = (ColVec2Mx p) * (LineVec2Mx q) iff ( len M = len p & width M = len q & ( for i, j being Nat st [i,j] in Indices M holds
M * (i,j) = (p . i) * (q . j) ) ) )