[alogo] Ellipse from circles

Given two circles A(R), B(r) such that their centers are at a distance [ d < R+r ], there is an ellipse [ (x/a)+(y/b)=1, look at Ellipse.html ] whose points C are at equal distances from the two circles. Its major axis (a) is the sum of the radii of the circles, (c) is |AB|/2 and b = c-a.

[0_0] [0_1] [0_2]
[1_0] [1_1] [1_2]


Switch to the [Select on contour] tool (Ctrl+2) catch and move C. The circles are controled using the [Selection] tool (Ctrl+1) and the points A, L, B and K. Look at the file ConicsFromCir.html for the general case.


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