You are not logged in.

 Discussion: All Topics Topic: Common Tangent Construction

 Post a new topic to the General Discussion in Geometry discussion
 << see all messages in this topic next message >

 Subject: Common Tangent Construction Author: Alan Cooper Date: May 8 2006
On Apr 10 2006, Mathman wrote:
(in another thread in the 'All Tools on a Calculator' Discussion)
> ...I taught mathematics, and found a lifetime of "rich imagery" in
> Euclid as well as all other studies.  Here's a simple example, and I
> wonder how it might be done differently or better without compasses
> and straightedge:

> The problem is to draw tangents to two circles.
> If the same size, there is no problem, the construction being
> basically a rectangle.  If one circle is noteably smaller than the
> other, there is a technique that is not too demanding, simple in
> fact.  If the circles are close in radii, but not equal, then the
> first is not possible, and the second is not feasible because of
> limit of distance required using the same technique, and the problem
> becomes a pretty problem [which I had solved and was able to
> demonstrate or offer to keen students.]

I thought it would be interesting to give a dynamic illustration of the
construction that (I presume) you had in mind.

The result is at http://www.langara.bc.ca/~acooper/mathlets/CommonTan

(This is not intended to replace the use of concrete drawing tools, but rather
just to make it possible for the student to see how the construction works in a
greater range of cases than it woud be possible to deal with by hand.)

Alan

 Reply to this message Quote this message when replying? yes  no
Post a new topic to the General Discussion in Geometry discussion
Visit related discussions:
Geometry

Discussion Help