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Topic: Perpendicular Lines
Replies: 3   Last Post: Jan 2, 2013 11:09 PM

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Guy Brandenburg

Posts: 83
Registered: 1/30/05
Re: Perpendicular Lines
Posted: Jan 2, 2013 10:00 PM
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att1.html (3.5 K)

I would use the fact that with a circle, tangent lines are perpendicular to radii. Find lines tangent to a circle at such-and-such a point on the circle in the plane...
Guy Brandenburg, Washington, DC

From: Fred Siegeltuch <>
To: "" <>
Sent: Wednesday, January 2, 2013 5:47 PM
Subject: Perpendicular Lines

Hi all,

I've seen tons of examples of math modeling where parallel lines arise and have a natural interpretation but I could use help in finding ones where the product of the slopes equals -1 is useful in modeling other than in doing bare geometry problems algebraically. I'd appreciate an example where this fact was used in such a way that covering this material didn't seem tangential (please forgive the pun) to a modeling perspective for algebra. I could try to embellish a problem that tries to find the tangent line to a circle or circular cylinder with a specific given radius but as of now I'm trying to do better. Ideally this should be no higher than the intermediate algebra level.


Fred Siegeltuch
City Colleges of Chicago

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