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Matrix multiplication
A multiplication of two matrices has the sequence
row 1 × column 1 row 1 × column 2 ··· row 1 × column m
row 2 × column 1 row 2 × column 2 ··· row 2 × column m
···
row n × column 1 row n × column 2 ··· row n × column m
Explanation
With a 2×2-matrix you can write the complex number z = a + bi as
When multiplying two complex numbers you get
Example 1
At multiplication of a complex number with its conjugate you get
and a check shows that this is true