# Xah Math Blog Archive 2013-11 to 2013-12

The Geometric Significance of Complex Conjugate (oldie but goodie)

### Vectors and Complex Numbers

complex numbers, or complex analysis, is one of the most beautiful math. If you don't know complex numbers, and you love geometry, it is essential you get to know it.

updated:

If you want to understand Einstein's theory of relativity, you must understand mobius transformation. To understand mobius transformation, you must first understand Riemann sphere, complex numbers, geometric inversion. Video and explanation at Stereographic Projection 3D-Printed Physical Model

### Astroid as Catacaustic of Deltoid

yay, my site made it to AMS blog. [• Astroid as Catacaustic of Deltoid By John Baez. At http://blogs.ams.org/visualinsight/2013/11/15/astroid-as-catacaustic-of-deltoid/ , Accessed on 2013-11-16 ]

it's written by the redoubtable mathematician John Baez. Baez is great, in that he writes serious math for any math undergraduate to appreciate, as opposed to many math popularizing authors who write for the laymen.

i did my curves project Visual Dictionary of Special Plane Curves mostly in 1994 to 1997, almost 2 decades ago, while i was a college student. I never seen the proof of how Deltoid's Catacaustic is a Astroid. I recall trying to, but it was too difficult for me back then. I haven't done much math since.

Do you know a proof of how Deltoid's Catacaustic is a Astroid? Post to John's g+ post. Thanks.

Ask me question on patreon