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Why j for Imaginary Unit?

· Big Data Zone


The symbols ij, and k are used for unit vectors in the directions of the xy, and z axes respectively. That means that “i” has two different meanings in the real plane, depending on whether you think of it as the vector space spanned by i and j or as complex numbers. But if you use j to represent the imaginary unit, its meaning does not change. Either way it points along the y axis.

Said another way, bold face and italic i point in different directions But bold face j and italic jboth point in the same direction.


And here’s what it looks like in electrical engineering notation:



By the way, I use j on @DSP_fact. DSP came out of electrical engineering, so j is conventional there. I also use j in Python because that’s what the language requires.


Published at DZone with permission of John Cook , DZone MVB .

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