[alogo] Parallels to ellipse

Construct the parallel-to-ellipse curves at distance x = AB. (red curve)
1) Select the tool from the menu-item [Curves \ Ellipse \ Ellipse( 2 foci + pt ) ].
2) Click two times 1st: at F, 2nd: at F' to define the two focal points of the ellipse.
3) Click at c to define a point on the ellipse. The ellipse with foci at F, F' appears.
4) Switch to the point-tool (CTRL + E).
5) Click near the ellipse, while holding down the SHIFT key. This sets point A exactly on the ellipse.
6) Select the tool from the menu-item [Shape-Tools \ Line Tools \ Tangent at _ _ ].
7) Click two times, 1st: at the ellipse, 2nd: at A. This sets the tangent t at A.
8) Select the tool from the menu-item [Shape-Tools \ Line Tools \ Orthogonal at _ _ ].
7) Click two times, 1st: at the line t, 2nd: at A. This sets the normal n at A.
8) Switch to the point-tool (CTRL + E) and click at B.
9) Select the [Geo Locus B(A)] tool from the toolbar. Click at A, then at B.
10) You get the path c', described by B as A glides on the ellipse.

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


1) Switch to the [selection-tool] (press CTRL+1). Catch and move points F, F', c, to change the shape of the ellipse.
2) Switch to the [pick-move-tool] (press CTRL+2). Catch and move point B. This changes the distance AB on the normal and this affects the shape of the parallel-to-ellipse curve c'.

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