Matrices: order, entries and special types
Read a matrix like a table: find an entry by its row and column, state its order and build the zero, identity and diagonal matrices.
- UK: Year 12
- France: grade 12
- Iran: grade 12
- Afghanistan: grade 11
- Palestine: grade 11
Guide
A matrix is a rectangular table of numbers in brackets. Its rows go across and its columns go down. The numbers inside are its entries.
The order (of a matrix) says how many rows and how many columns: rows first. A matrix with 3 rows and 4 columns has order 3×4. The entry in row i and column j is written aᵢⱼ.
A matrix with as many rows as columns is a square matrix. Its diagonal runs from top left to bottom right. In a diagonal matrix everything off the diagonal is 0. The identity matrix I is the diagonal matrix with 1 on the whole diagonal.
Matrices are written left to right here, with round brackets, as in the Afghan book. Ask: how did you know it was that entry? Rows first, columns second is the habit to build.