0:04 so today we're going to be learning about
0:04 about matrices
0:15 and a matrix is the singular form of matrices
0:16 matrices
0:19 it just means one matrix but if you're
0:20 talking about
0:23 matrices you're probably talking about
0:25 two or more since it's plural
0:28 now a matrix is simply going to be a rectangular
0:29 rectangular
0:34 array a rectangular array
0:39 of elements a rectangular array
0:49 now what this means is you're going to
0:50 have a box
0:53 it's going to have brackets sometimes it
0:55 has parentheses but this one is going to
0:56 have brackets
0:58 and this matrix is going to have two
1:01 rows and two columns
1:03 the first row is going to be seven eight nine
1:05 nine
1:07 and the second row is going to be one two
1:08 two
1:12 three so given this matrix
1:17 we know that it has two rows two rows
1:19 but we also know that it has three columns
1:21 columns
1:23 so what i'm going to do is i'm going to
1:26 change my color to red and i'm going to circle
1:26 circle
1:30 all the rows i'm going to circle all the rows
1:31 rows
1:33 so this is going to be the first row
1:34 this 7
1:38 8 and 9 and then the second row
1:42 is going to be one two three
1:45 so rows are always going to go from left
1:46 to right
1:48 they're always going to go from left to
1:49 right so they
1:53 are horizontal in a sense
1:56 now i'm going to change my color to blue
1:57 and i'm going to circle
1:59 all the columns so this is going to be
2:01 the first column
2:04 7 1 this is going to be the second column
2:06 column
2:09 8 2 and this is going to be
2:12 the third column 9 3
2:15 so columns are always going to go from up
2:16 up
2:19 to down so these are going to be
2:22 vertical okay
2:25 now that's the difference between rows
2:26 and columns
2:29 and what we do is we can specify a dimension
2:30 dimension
2:33 so a dimension let me put my color back
2:34 in white
2:36 what we're going to be doing is we're
2:38 going to be defining the dimension of a matrix
2:47 all right now this is going to be two
2:48 numbers you're going to have a row number
2:49 number
2:53 times a column number and r just means
2:55 how many rows you have
3:03 and c is going to be the number of columns
3:16 so here our matrix has two rows
3:23 and then since it has three columns the
3:27 c number is going to be a three
3:30 so this is a two by three matrix we say
3:33 it has two rows and three columns
3:35 and then the last thing we can do is we
3:37 can specify
3:40 the entry that we're looking at so let's
3:41 say i want to specify
3:44 this number eight right here well
3:46 what i would have to do is first i would
3:48 have to give this matrix a name
3:51 let's say it's matrix m and that's a
3:53 capital m by the way
3:56 what we would do is we would write a lowercase
3:56 lowercase
4:00 m standing for an entry of matrix
4:02 m and then we would have to specify the
4:04 row number and the column number
4:08 so this eight is in the first row
4:11 so the row number is going to be one but
4:14 it's also in the second column right
4:18 so the column number is going to be 2.
4:21 so m12 is going to be equal to
4:24 8. so if you know the row number
4:27 and you know the column number you can
4:28 specify any
4:31 element in this matrix and the elements
4:33 are just going to be the numbers
4:37 inside the matrix so that's matrix
5:06 [Music] you
