1. Congruent triangles – Part 2 Slideshow 39, Mathematics Mr Richard Sasaki, Room 307

2. Objectives Understand and recall some shape properties (in particular the right-angled triangle) Practice showing whether triangles are congruent or not using rules given last lesson Introduce Similar Triangles

3. Edges, Vertices and Faces Vertex (plural: vertices) Edge Face – Used more with 3D objects

4. Right-Angled Triangle Each edge has a special name for a right- angled triangle in respect to another angle. Hypotenuse Opposite Adjacent

5. Triangle Congruency Testing Rules We have learned 4 laws to test congruency. Which is which? SS S SA S RH S AAcor S

6. Notation & Definition Recall that if the two triangles below are congruent… A B CX Y Z We can say either… We can’t say ∆ABC ≅ ∆XZY

7. Example Explain why ∆ABC and ∆ADC are congruent. B A C D Note: The dots “●” represent given angles that are the same size. ∆ABC ≅ ∆ADC by SAS as… BC = DC,

8. Answers

9. Similar Shapes What are similar shapes? Similar shapes are the same shape…but don’t have to be the same size. These shapes are similar.

10. Similar Shapes To be the same “shape”, the shapes must be in the same proportion. These shapes are not similar. Note: Congruent shapes are also similar shapes. If the size is also the same, they are still similar.

19. These two triangles are similar. A B Triangle A and B have heights 4cm and 6cm respectively. If triangle A has base 5cm, what is the base of triangle B? 4cm 6cm 5cm ? 4cm : 6cm 2 : 3 5cm : ____ x 2.5 7.5cm

20. 10cm 3cm 1. Split the rectangle into 2 similar rectangles that are not congruent. 9cm 3cm 1cm 2. Prove that the flashing length is 3cm using the method in Question 1.