Euler's formula from the Taylor series
Proof of Euler's formula in eight steps: the Taylor series of eˣ only needs plus and times and therefore also works for complex numbers. With z = iφ every term turns another 90°, and the arrows form a spiral towards the unit circle. Sorted into terms without and with i, they become the series of cosine and sine, shown on a helix with cos and sin shadows. De Moivre's theorem follows at the end.
Complex numbersTry it