Euler's paper for the theorem $ e^{i\theta} = \cos(\theta) + i\sin(\theta) $?

Question

Which is Leonard Euler's Paper where he proves this central result? The term 'complex number' does not seem to have been used by him. I'm hoping someone could link me to some page in the Euler archive.

For the term "complex number", see Earliest Known Uses of Some of the Words of Mathematics : COMPLEX NUMBER.: "Most of the 17th and 18th century writers spoke of $a + bi$ as an imaginary quantity. The term complex number was used in English in 1856 by William Rowan Hamilton." — Mauro ALLEGRANZA, Jul 05 '16 at 14:44
This older question seems closely related: Euler's first proof of $e^{ix}=\cos(x)+i\sin(x)$ — Martin, Jul 11 '16 at 10:40
@MauroALLEGRANZA I wonder if you would have any thoughts on How did the definition of complex logarithm evolve since Cotes (1682-1716)? — uhoh, Mar 31 '19 at 02:41

Mikhail Katz · Accepted Answer · 2016-07-05T14:43:56.707

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This appears at the end of $\S\,138$ in Introductio (1748). In Blanton's translation this appears on page 112, line 5.

edited Jul 05 '16 at 14:43

answered Jul 05 '16 at 13:15

Mikhail Katz

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I think Introductio (1748)... – Mauro ALLEGRANZA Jul 05 '16 at 14:40

Euler's paper for the theorem $ e^{i\theta} = \cos(\theta) + i\sin(\theta) $?

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