Published online by Cambridge University Press: 01 August 2016
A vivid memory of mine is of being shown that certain 2 × 2 matrices were ‘really’ complex numbers. The correspondence between matrices of the form
and complex numbers
seemed magical and the additional remark that
was an unexpected bonus. The correspondence has been examined in various articles in the Gazette [1, 2]. That it is an isomorphism is seen by comparing
with
in the case of addition, and, in the case of multiplication, by comparing
with