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Comments by @pgrosser1:
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- It would be useful at the very start to define what a complex number is, ie.
$i = \sqrt{-1}$ or equivalently the solution to the quadratic equation$x^2 + 1 = 0$ . Then we could say something along the lines of: Clearly, this is not part of our repertoire of real ordinary numbers, because we expect that squaring a number will always make it positive and therefore there is no$x$ that should satisfy$x^2 + 1 = 0$ . Hence, we must introduce a new mathematical formulation called complex numbers… - Give a graphical representation at the start when introducing the various forms of a complex number so that the values
$x$ ,$y$ ,$r$ , and$\theta$ can be visualized and related. - It could be useful to show how trigonometric functions in terms of complex numbers come out of the definition
$e^{i \theta} = cos \theta + i sin \theta$ (would take approximately 2 lines to show, so it is brief and allows for some familiarity with Euler’s formula before examples are introduced). - A note in 6.3.5 that
$i$ can be treated as a constant (which it is anyway, but just for clarity’s sake) when integrating and differentiating might assist. Again, I don’t think the code at the end of 6.3.5 presents a very intuitive verification, and a graphical representation (as outlined above) would be more helpful.