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### Uses of Ellipses

```Date: 04/02/2003 at 20:54:06
From: Rachel
Subject: Uses of Ellipses

I see there are examples of conic sections in daily life on this
site, but I can't find ellipses. How are ellipses used in real life?
```

```
Date: 04/03/2003 at 14:16:13
From: Doctor Douglas
Subject: Re: Uses of Ellipses

Hi, Rachel,

In addition to the astronomy applications mentioned in

Who uses Ellipses?
http://mathforum.org/library/drmath/view/54787.html

Here are some other places where you will find ellipses:

The shape of a spotlight on a planar surface is in most
cases an ellipse. In some cases it may be a circle.

If you cut a cylinder at an angle, you will get elliptical
sections. This can have important applications in optics
(lenses and mirrors can be elliptical in shape), or in the
kitchen (where one might cut vegetables or sausage along a
"bias cut" in order to obtain pieces that have the same
thickness, but have more surface area exposed.

Some tanks are in fact elliptical (not circular) in cross
section. This gives them a high capacity, but with a
lower center-of-gravity, so that they are more stable when
being transported. And they're shorter, so that they can pass
under a low bridge. You might see these tanks transporting
heating oil or gasoline on the highway

The ellipse is found in art and architecture, and you may be
familiar with the Ellipse, part of a President's Park South
(a National Park in Washington, DC, just south of the White
House).

Ellipses (or half-ellipses) are sometimes used as fins, or
airfoils in structures that move through the air. The
elliptical shape reduces drag.

On a bicycle, you might find a chainwheel (the gear that is
connected to the pedal cranks) that is approximately elliptical
in shape. Here the difference between the major and minor
axes of the ellipse is used to account for differences in the
speed and force applied, because your legs push and pull more
effectively when the pedals are arranged so that one pedal is
in front and one is in back, than when the pedals are in the
"dead zone" (when one pedal is up and one pedal is down).

- Doctor Douglas, The Math Forum
http://mathforum.org/dr.math/
```
Associated Topics:
High School Conic Sections/Circles
Middle School Conic Sections/Circles

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