00:02
We are given that a is a block diagonal matrix, a0, 0, 0, 0, b not, where a0 and b not are diagonal block matrices, and we are asked to prove that e to the at has a certain form.
00:31
Since a is a block diagonal matrix, we have that a is going to be, call it an n -by -n matrix, and since a -0 and b -0 are both diagonal block matrices except with diagonal, we have that a -0 is going to be an element to some m by m said matrices, and e -0 of some m by l, or l by l matrices.
01:20
But a -0 and b -not are also both diagonal, so that, say, a -0 is going to be the diagonal matrix, with entries and what this 01 is the same the entry that is that to a sub i j, then a s of i j is going to be equal to.
02:47
We have three different cases.
02:58
It lies in the diagonal so that i is equal to j, and we have that i is less than or equal to m.
03:17
Then we have that a i j is going to be the diagonal entries of a not, which is going to do a not and then i or a not j because they're the same and if we're still on the diagonal so that i equals j but now we have that n plus 1 is less than or equal to i is less than or equal to total which is n and we have that a i j is equal to b not i and finally i is not equal j so this is simply going to be 0.
04:14
So we see that we do have a diagonal matrix here...