00:01
In this problem, we are given an n -by -n matrix whose diagonals.
00:09
It means that the only non -zero values of this matrix lie on the main diagonal, and the other values, the other entries outside the main diagonal, are zero.
00:21
So this triangle over here and this triangle over here is zero.
00:29
So the goal is to compute the exponential matrix e to the point.
00:33
So let's start.
00:38
The first step is then to compute the powers of the matrix a.
00:46
So a to the power k is the multiplication of the matrix a with itself k times.
00:56
So we are going to use a mathematical way of proving that is the technique of induction.
01:05
So if we want to compute a to power k in general where k is an integer, so we start with a square of this.
01:13
So what is a square? so if this matrix r1, r2, rn, so all these values are 0 times itself r1, r2, up to rn, so when we multiply this matrix, we get r1 square in the first entry, this row times this column.
01:40
Is just r1 square this row times the second column that that brother is zero zero here we get zero arc two square zero and finally we get our n square okay so the square of our matrix is given by the square of each entry on the main diagram so how about a to power k so we will suppose we will assume that a to the power k minus one is the matrix whose entries in the diagonal are given by the k minus one powers of our initial diagonal entries and this is zero else one okay so then we need to compute a k that using this formula is the same as a times a power k minus one just by grouping up all these final k -1 factors of a.
02:59
So this is a times a k -minus -1.
03:03
So we will do this matrix multiplication a to the power k is the matrix a, r1 -0, r2 -0, and that is only the value r -i in the i position of the diagonal, times, and then the value, and the the value, and the the one, the the matrix a to the power k minus one which is r1 to power k minus 1 0 0 here we get r to the color k minus 1 0 here r nk minus 1 okay so when we multiply this column by this row we get r1 to the power k when we multiply the first column first row by the second column we get zero and so on.
04:02
So then we'll multiply the second row by the first column.
04:07
We get zero.
04:08
Here we get arc to power k, zero.
04:14
And so zeros.
04:16
And finally, the last entries are into the power of k...