Date: Tue 10.11.98 20:00
From: Alex Bogomolny
The trigonometric identity you forgot is de Moivre's formula:
https://www.cut-the-knot.com/pythagoras/cycloids.shtml#demoivre
Think of the angle for which the formula results in "i" on the left. Then raise both sides to the power of "i": i^i = e-Pi/2.
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