Quote Originally Posted by Acorn View Post
Nice to watch Marco.

You are solving these faster than I can make them!

My solution uses the ellipse, a circle and a line.

  1. Create a Green circle, a Blue Line and a Red ellipse, all 400px wide; the Red ellipse can be a clone of the Green circle, halving its Height.
  2. Place the circle and ellipse bases together; the circle's centre is now on the ellipse edge. the length of a radius to either of the points where the line cuts the circle are, necessarily, 200px. The chord, the line in the green, is what we want.
  3. Select the line and circle and Intersect.
  4. Switch to the Shape tool after selecting the chord (this is a shape and not a line); it has zero Line size.
  5. Click on the chord to add a Node.
  6. Drag the Node to any point of the Red ellipse.

Focal Points Ellipse.xar

Instead of a line, I halved a cloned ellipse to the same effect. I found the line solution clearer.

Acorn
You solution is indeed clearer. I hadn't tought interecting a line with a shape (the circle in this case), good to know!
Next time I'll try to wait a bit longer before posting my solutions

Marco.