Definition:Imaginary Unit/Also denoted as
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Imaginary Unit: Also denoted as
The non-italicized $\mathrm i$ can also be seen.
Using the formal definition of complex numbers, the imaginary unit is the ordered pair $\tuple {0, 1}$.
When mathematics is applied to engineering, in particular electrical and electronic engineering, the symbol $j$ is usually used
This is because $i$ is the standard symbol used to denote the flow of electric current, and to use it also for $\sqrt {-1}$ would cause untold confusion.
In some mathematical traditions, the Greek symbol $\iota$ (iota) is used for $i$.
Sources
- 1990: H.A. Priestley: Introduction to Complex Analysis (revised ed.) ... (previous) ... (next): $1$ The complex plane: Complex numbers $\S 1.1$ Complex numbers and their representation
- 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): complex number
- 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): complex number