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.

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الدليل

A مصفوفة ⁦is a rectangular table of numbers in brackets⁩. ⁦Its rows go across and its columns go down⁩. ⁦The numbers inside are its entries⁩.

The رتبة ⁦says how many rows and how many columns⁩: ⁦rows first⁩. ⁦A matrix with 3 rows and 4 columns has order ٣×٤⁩. ⁦The entry in row i and column j is written aᵢⱼ⁩.

⁦A matrix with as many rows as columns is a⁩ مصفوفة مربعة. ⁦Its diagonal runs from top left to bottom right⁩. ⁦In a diagonal matrix everything off the diagonal is 0⁩. The مصفوفة الواحدة ⁦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.