00:01
Okay, so let's prove for the both direction of this statement.
00:05
And let's just first take the forward direction.
00:07
That is, if a is equal to 0, then trace a to the t times a is equal to 0.
00:14
So, assume that a is a m times n matrix with real entities such as a equal to 0.
00:20
And we want to show that the trace a to the t times a is equal to 0.
00:24
The transpose of the 0 matrix is still 0 matrix.
00:27
So, we have a to the t equal to 0.
00:30
Now consider the product a of t times a that is a to the t times a equal to 0.
00:36
The trace of the zero matrix is the sum of its diagonal entries which are all zero.
00:41
Therefore the trace of a to the t times a is equal to 0.
00:47
Then if a is equal to 0 so this is also equal to 0...