- Star Tales - Corona Australis (ianridpath.com)
Corona Australis was known to the Greeks not as a crown but as a wreath, which is how it is depicted on old star maps. Aratus did not name it as a separate constellation but referred to it simply as a circlet of stars beneath the forefeet of Sagittarius. Hyginus said it was a wreath cast off by the archer ‘as by one at play’.
- Euler’s formula (Wikipedia)
Euler’s formula, named after Leonhard Euler, is a mathematical formula in complex analysis that establishes the fundamental relationship between the trigonometric functions and the complex exponential function. Euler’s formula states that, for any real number x, one has eix = cos x + i sin x, where e is the base of the natural logarithm, i is the imaginary unit, and cos and sin are the trigonometric functions cosine and sine respectively. This complex exponential function is sometimes denoted cis x (“cosine plus i sine”). The formula is still valid if x is a complex number, and is also called Euler’s formula in this more general case.
- Corona Australis (Wikipedia)
Corona Australis is a constellation in the Southern Celestial Hemisphere. Its Latin name means “southern crown”, and it is the southern counterpart of Corona Borealis, the northern crown. It is one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one of the 88 modern constellations. The Ancient Greeks saw Corona Australis as a wreath rather than a crown and associated it with Sagittarius or Centaurus. Other cultures have likened the pattern to a turtle, ostrich nest, a tent, or even a hut belonging to a rock hyrax.
