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Naming the Isosceles Triangle

Date: 09/23/98 at 23:44:24
From: Caron Harris
Subject: Isosceles triangle name

One of my 7th grade reading students wanted to know how the isosceles 
triangle received its name.

Date: 09/24/98 at 04:05:26
From: Doctor Mike
Subject: Re: Isosceles triangle name
The mystery can be resolved by looking in almost any good dictionary.
The word is of Greek origin, coming from isos, meaning equal, and 
skelos, meaning leg. Looking up the etymology of a word or two in
a reading assignment would be a good habit to encourage for your 7th 
graders. Are you actually using material with some mathematical content 
for general reading instruction? Fantastic!  
- Doctor Mike, The Math Forum   

Date: 09/24/98 at 07:28:29
From: Darla or Caron
Subject: Re: Isosceles triangle name

Thank you. We thought maybe there was more to it than just that. You're 
right; I also found that in a dictionary. In our reading classes, we 
teach all subjects and hit on all disciplines. Thanks again.


Date: 10/07/98 at 13:06:31
From: Doctor Mike
Subject: Re: Isosceles triangle name

Hello again, Caron,
You're very welcome. You may be right, too. Many words of Greek or 
Latin origin are thoroughly modern inventions, like "isotope," which
relate to scientific concepts not known to the ancients. However it
appears that isosceles is somewhat different.  
My dictionary says that isosceles is an actual Latin word, coming from
the actual Greek word isoskeles. This makes sense really. The Greeks
pretty much owned geometry back then, so they must have had a word for
this. They would have used the same roots "isos" and "skelos" to form 
the word. But since the concept was known to them, we didn't have to 
wait for modern mathematicians to invent the word.  
From my very limited knowledge of Greek, I'm pretty sure Euclid and
the others did not pronounce it the same, probably something sounding
like EE - SO - SKAY - LEASE.  To me it is sort of neat to know I am
saying the same word that they were using for this idea 2500 years ago!  
By the way, the word "scalene" for a triangle with 3 different leg 
lengths comes from another Greek word "skalenos" meaning uneven.  
I was mentioning this question to one of my kids, who clued me in to 
the interesting etymology for helicopter. The two Greek roots are the
same as for HELIx and PTERodactyl. Next time you are reading about 
flying things from Jurassic to Modern times this could come in handy.
Thanks for writing. 

- Doctor Mike, The Math Forum   
Associated Topics:
High School Geometry
High School History/Biography
High School Triangles and Other Polygons
Middle School Geometry
Middle School History/Biography
Middle School Triangles and Other Polygons

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