The 'Why': Why do we need to be able to draw triangles?
This lesson starts by asking students to attempt to identify how many triangles there are inside a drawing of a larger triangle. This will likely lead to quite a bit of debate. Suggest that students try it on their own before the register and then they can discuss and settle on an answer. An image displaying all of the solutions will display when you click.
As with the previous lesson, what follows is a slide about the history of mathematics, in this case; Pythagoras of Samos and his influence on geometry. Students are asked to make a quick factsheet that takes up a small amount of room in their books and write down some of the facts featured on the short video.
Slide 5 is a recap of the geometric instruments from the previous lesson and serves as a good opportunity to double check that all students have them. After this is a quick explanation of the importance of the triangle to the world of architecture. There is a model showing what would happen if this were a square and how squares are often reinforced to make two triangles. This allows students to understand the importance of being able to construct an accurate triangle without the assistance of a computer. There are then some examples so that students can see this in action.
There are then 3 types of triangle to cover; SSS, SAS and ASA. Each type is covered individually with a full size example that students can copy along with. Alternatively, you could show the students the whole process once and then get them to copy along the second time. There is then 8 for them to try with a worded question as an extension on each.
Lastly, there is a task getting students to cut a piece of paper diagonally into 4 triangles and then reassemble them into as many different alternate shapes as possible. This is a great example of another way to create a template for an equilateral triangle and links back to the starter of this lesson.
Activities included:
How many triangle?
History of Mathematics
Geometric Tools
The importance of the triangle and architecture
How to construct triangle
Triangle Investigation