If you take a circle, say 12ft in diameter, and mark it out like a clock face, standing face on to it, it will appear circular. If you then rotate the circle 45 degrees about the 6 – 12 axis it will appear elliptical, but is this a regular ellipse?

Viewing the circle at this angle, the chord distance between the 8 o’clock and 10 o’clock marks will appear greater than the chord distance between the 4 o’clock and 2 o’clock marks as the 4 – 2 chord is further away.

This means that the curve length 12 – 3 – 6, appears less than the curve 12 – 9 – 6 so the ‘ellipse’ has one side shorter than the other.

Can anyone explain this to me please?