Re. circle around an ellipse

[ptc-3352045]

Hi! All,

I thing I had better explain the probblem more fully,

The centre of an ellipse is at (0,0) with it's major axis along the X axis, let the semi major axis be "a". long. At a point "o" along the positive X axis at say "2a" distance from (0,0) is the centre of a circle drawn tangent to the outside of the ellipse, this line along the positive X axis joining the two centres,is rotated in a counter clockwise direction carring with it the circle, but the circle must remain tangent to the outside of the ellipse. obviously to do this the distance between the two centres must be continuously changing, So herin is the problem, to find this length at any given rotation of the line joinging the two centres??

Regards Brian

[Fred_Kohlhepp · Accepted solution]

This is what Valerie (very elegantly) and I have both done.

The last graph in my sheet is center distance vs angle.

[Fred_Kohlhepp]

One more pass:

[ptc-3352045]

Thank you Fred, I was trying to do the problem from a purely polar co-ordinate sytem, but I see now

" thank's to you " that it needs to be done from a cartesian sytem and differentiating the equation of the ellipse.

Brilliant Fred I can do it now

Regards Brian

PS. Great video, I'd love to know the maths how you did that

[Fred_Kohlhepp]

PS. Great video, I'd love to know the maths how you did that

The sheet that shows you the math creates the avi. Look up "animate" under tools. Rresearch FRAME in help.