What are the characteristics of an ellipse?

Answer 1

Here's one way to think about an elllipse:

-- Mark two black dots on a piece of paper, or stick two nails into a piece of wood.

-- Mark a dot anywhere else on the paper, just not on the line between the

first two.

-- Measure the distance of the new dot from the first one, and from the second one,

then add those two distances.

-- If you draw another dot at every place on the paper where the sum of the

two distances from the first two dots is the same sum, you'll have an ellipse.

-- The first two black dots, or the nails, are the foci (focuses) of the ellipse.

-- The farther apart the first two black dots are, the more eccentric the ellipse is ...

skinny compared to its length.

-- When the first two black dots get so close together that they're the same dot,

then you have an ellipse whose eccentricity is zero, and there's a special name for

that ellipse. It's called a 'circle'.

Easy way to draw it:

-- Tie a piece of string in a loop.

-- Drop the loop of string around the two nails.

-- Put a pencil point into the loop. Pull it out to the side until there's no slack in the loop.

-- Run the pencil around, keeping it against the string with no slack in the loop.

You're drawing an ellipse.

If you pull out one nail, you're drawing a circle.