1. to find angles in special triangles
Triangles and Quadrilaterals
Objectives:
to find angles in special triangles
To calculate the degrees in a quadrilateral

2. What do you notice about the angles in a triangle?
A straight line
Allow 10 minutes for this activity esp giving out paper, issuing scissors and checking classwork.
What do you notice about the angles in a triangle?

3. ? 30° To find the missing angle 180° – (sum of given angles) = ?
Angles in a Triangle always add up to 180° ?
70°
30°
To find the missing angle
180° – (sum of given angles) = ?
Copy this diagram and rule into your books – allow 3 minutes.
180° - 70°- 30° = 80°

4. Find the missing angles a, b, c and d.
30°
45°
20° a
60° b
63°
29°
Sketch diagrams – not accurate but with a ruler pls - and answers with workings allow 10 minutes. NB Right angle notation. c
72° d

5. Equilateral Triangle The angles are always 60° All angles are equal.
All Sides are equal
The angles are always 60°

6. Isoceles Triangle
2 angles are equal.
2 Sides are equal

7. Right – Angled Triangle
1 angle always 90°
2 other angles = 90°

8. Scalene Triangle
No Equal Sides
No Equal angles

9. Find the missing anglesb
80̊ a
120̊
Sketch diagrams – not accurate but with a ruler pls - and answers with workings allow 10 minutes. NB Right angle notation. c d
30̊

10. Can you work out the missing angle a?
Plenary……Finding missing angles using 2 x angle facts - GCSE Grade “E” Skill

11. What do all of these shapes have in common?
Plenary……Finding missing angles using 2 x angle facts - GCSE Grade “E” Skill

12. Can you work out the missing angle b?
115 ̊
115 ̊
Plenary……Finding missing angles using 2 x angle facts - GCSE Grade “E” Skill
65 ̊

13. Odd one out?
40, 40, , 50, , 40, 110
35, 45, , 60, , 20, 70

14. 1. Triangles can have more than 1 obtuse angle
Sometimes, Always, Never
1. Triangles can have more than 1 obtuse angle
2. A right angled triangle can also be an isoceles angle
3. A triangle with a 60º angle is an equilateral
4. There are two triangles in all 4 sided shapes