Elements of a triangle

Elements of a triangle are the angles that are formed when three lines intersect and the segments that mark the triangle are sides.

Prior knowledge of point, lines, angles, parallel lines

Digital : Computer, geogebra application, projector.
Non digital : Worksheet and pencil,6-8 strings (preferably in different colours)
Geogebra files : “Elements of a triangle.ggb”

Students work individually but in their groups.
Take the strings and place them in such a way as to make a closed figure.
What is the smallest number of strings with which you can form a closed figure?
What is this figure called?
Can you just draw the lines along the strings and see what you get?
When you drew, what did you draw? (Was it a line or was it an angle or was it a line segment?). It is a lime segment – how many line segments are there?
When two line segments joined, what is it called? (A vertex). How many vertices are there?
Is there any angle formed when you made this figure? How many angles were formed?
Show a simple Geogebra file with triangles – Use this file to demonstrate that every triangle has the elements - vertices, sides and angles
How many triangles were formed? Were there any strings left over?
For each of the triangles trace the shape on the book and write down the elements of the triangle in the following format

For each of the triangles observe (inspect visually) which is the longest side and which is the shortest side

Allow the students to explore if there is any connection between the two?
After the students see the Geogebra file, they can attempt an alternative worksheet like below

Side 1	Angle 1 (opposite angle)	! Side 2	Angle 2 (opposite angle)	! Side 3	Angle 3 (opposite angle)	! Largest side and angle ex-side1,angle1	! Smallest side and angle ex-side3,angle3

Have the students been able to identify the elements in a triangle?
Have they been able to extrapolate any connection between the angle and side in a triangle?

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