theorem Th71: :: MATRIXJ1:71

for K being Field
for a1, a2 being Element of K
for A1, A2, B1, B2 being Matrix of K st len A1 = len B1 & len A2 = len B2 & width A1 = width B1 & width A2 = width B2 holds
(block_diagonal (<*A1,A2*>,a1)) + (block_diagonal (<*B1,B2*>,a2)) = block_diagonal ((<*A1,A2*> (+) <*B1,B2*>),(a1 + a2))