We can draw an ellipse using a piece of cardboard, two thumbtacks, a pencil and string. Place the thumbtacks in the cardboard to form the foci of the ellipse Cut a piece of string longer than the distance between the two thumbtacks
(the length of the string represents the constant in the definition). Tack each end of the string to the cardboard, and
trace a curve with a pencil held taut against the string. The result is an ellipse.
1) Show that d1+d2=2a. Send
pictures for this question.
(use a ruler after drawing your
ellipse)
*
Foci