article
Squareo'scope determines the kind of triangle
A description of some experiments in which you can make discoveries about triangles.
Triangles
-
-
articleIncircles explained
This article is about triangles in which the lengths of the sides and the radii of the inscribed circles are all whole numbers. -
articleLiethagoras' theorem
Liethagoras, Pythagoras' cousin (!), was jealous of Pythagoras and came up with his own theorem. Read this article to find out why other mathematicians laughed at him. -
articleInteracting with the geometry of the circle
Jennifer Piggott and Charlie Gilderdale describe a free interactive circular geoboard environment that can lead learners to pose mathematical questions. -
pageMaking maths: equilateral triangle folding
Make an equilateral triangle by folding paper and use it to make patterns of your own. -
pageMaking maths: test the strength of a triangle
Have you noticed that triangles are used in manmade structures? Perhaps there is a good reason for this? 'Test a Triangle' and see how rigid triangles are. -
articlePeg and pin boards
This article for teachers suggests activities based on pegboards, from pattern generation to finding all possible triangles, for example.
-
problemThree fingers and a loop of string
Age5 to 7Challenge level
Using a loop of string stretched around three of your fingers, what different triangles can you make? Draw them and sort them into groups. -
problemArea i'n it
Age16 to 18Challenge level
Triangle ABC has altitudes h1, h2 and h3. The radius of the inscribed circle is r, while the radii of the escribed circles are r1, r2 and r3 respectively. Prove: 1/r = 1/h1 + 1/h2 + 1/h3 = 1/r1 + 1/r2 + 1/r3 . -
problemFitting in
Age14 to 16Challenge level
The largest square which fits into a circle is ABCD and EFGH is a square with G and H on the line CD and E and F on the circumference of the circle. Show that AB = 5EF. Similarly the largest equilateral triangle which fits into a circle is LMN and PQR is an equilateral triangle with P and Q on the line LM and R on the circumference of the circle. Show that LM = 3PQ