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ERIC Number: EJ859744
Record Type: Journal
Publication Date: 2009-Sep
Pages: 5
Abstractor: ERIC
Reference Count: 6
ISSN: ISSN-0025-5785
Centres and Circles of a Triangle
Forsythe, Sue
Mathematics Teaching, n215 p9-13 Sep 2009
In this article, the author describes an activity she has used with two different groups: (1) high attaining year 8 children; and (2) Secondary Mathematics PGCE students. In the activity they created what was, ostensibly, the same geometrical objects using paper folding, pencil, ruler and compasses, and the "Geometer's Sketchpad"--an example of Dynamic Geometry Software (DGS). Then the author reflected upon these activities, on the differences in the methods used, and the geometrical concepts underpinning them. In this activity they created the perpendicular bisectors of a triangle. It was noticed that the perpendicular bisectors meet at one point and they used this point as the centre of the circle which goes through the vertices of the triangle. Similarly they found the angle bisectors of a triangle and used their point of intersection to draw the inscribed circle. It has to be said that the students needed to be told to draw the circumcircle and the inscribed circle--the author did not give them the opportunity to discover them for themselves. However, students were interested to find that they could indeed draw these circles.
Association of Teachers of Mathematics. Unit 7 Prime Industrial Park, Shaftesbury Street, Derby, DE23 8YB, UK. Tel: +44-1332-346599; e-mail:; Web site:
Publication Type: Journal Articles; Reports - Descriptive
Education Level: Grade 8; Secondary Education
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A