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24-Ruby IV
October 11, 2020
Question

Sinusoid or not sinusoid

  • October 11, 2020
  • 1 reply
  • 1967 views

It is a sinusoid:

sin-XY.png

Is it a sinusoid or this curve has any other name?

sin-Polar.png

I will not sleep until I get an answer!

1 reply

25-Diamond I
October 11, 2020

Its a Cardioide! Try sin(x)-1 instead of sin(x) and use a regular polar plot (with zero in the centre).

Werner_E_0-1602458231371.gif

 

You may see it every morning on the surface of your cup of coffee because the caustic of a circle is a Cardoide.

https://en.wikipedia.org/wiki/File:Caustique.jpg

24-Ruby IV
October 14, 2020

My method to animate the cardiod

Cardioid.png

25-Diamond I
October 14, 2020

What your pic shows is an Epicycloid (or Hypercycloid).

Most of them don't have special names.
Only if r1=r2 its called a Cardioid and if r1=2*r2 its called a Nephroid.

 

If a circle rolls INSIDE another, the path is called a Hypocycloid.

 

And if you watch for the path of a point not on the perimeter of the circle, its called a trochoide.