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Details of Class: Lesson 1 Date: Time: 50mins Learning Intentions/Topic: Year: 8 Geometry: Triangles To recognise different types of triangles and their properties To be able to draw all different types of triangles, labelling sides and angles correctly Room: No. of students: Relationship to VELS: Classification of polygons with reference to a definition or key property Using language relevant to the topic Resources Required: Students to each have their own workbook and stationery Maths Quest 8 textbook Student Activities worksheet/questions (attached) Matches or item of similar size (15 per student) Introduction/Housekeeping/Warm-up: Introduction to Geometry: Who knows what Geometry is? Pg. 234 text – geometry comes from Latin geo meaning earth and metre meaning measure. Considered geometry as a science of measuring our Earth and describing its properties. Geometry today looks at angles, shapes and solids, and investigates their relationships and properties. 5 mins Content Resources Time What is a triangle? - 3 sides: tri means three. Triangle = three angles - ‘Give Way’ signs - Identify other everyday triangle-shaped things 2 min There are different types of triangles. Triangles can be named according to the length of their sides or the size of their angles. Go through ‘Naming Triangles’ together as class describing types of triangles and their properties. Classification: What is a right-angle? A. An angle of 90° What is an acute angle? A. Angle less than 90° What is an obtuse angle? A. Angle greater than 90° 7 min Text p.235 Important note: To indicate the sides of equal length and angles of equal size, we use identical marks. To indicate that the angle is right (90°), a small square is used. *Draw examples on whiteboard and point out symbols/markings that are used and what they mean. Activity: Students to complete table of triangles from ‘Student Activity’ sheet with the help of the information on p. 235 Get students to draw certain types of triangles on the board using correct side and angle markings where appropriate. Allow students to explain the drawing to their classmates, and allow classmates to help if student is unsure. 3 min ‘Student Activity’ sheet – triangle table 10 min 6 mins Students to complete activities 2-5 from question sheet. ‘Student Activity’ Hand out matches (or similar) to students to allow them to complete questions 4, 5 and extensions. Students can work in pairs for these match stick tasks although all students must copy answers into each of their workbooks. Matches 14 min Reinforcement of Ideas/Questioning/Homework: Collect matches Homework is to complete any questions which were not finished in class. If you do not have any matches at home to help complete questions, use pens, pencils, cutlery, or other similar objects instead. 3 mins Overall reflection of lesson: Student Activities: Triangles 1. Complete the table. Keep completed table for your own reference. Picture Name of Triangle Definition Equilateral Triangle One angle is greater than 90° Scalene Triangle All angles are less than 90° Student Activities: 2. Using side and angle markings where appropriate, draw a triangle that is: a) Right-angled b) Isosceles c) Obtuse-angled d) Scalene 3. Using side and angle markings where appropriate, draw a triangle that is: a) Both right-angled and scalene b) Both acute-angled and isosceles c) Both obtuse-angled and isosceles d) Both acute-angled and equilateral (Students can work on their own or in pairs for the following activities) 4. Using 12 matches, construct each of the following triangles. Draw the solutions in your workbook, clearly showing the number of matches used on each side. a) An equilateral triangle b) A scalene triangle c) An isosceles triangle 5. Use matches to construct each of the following structures. Draw the solutions in your workbook. a) Use 9 matches to make 3 equilateral triangles b) Use 8 matches to make 3 equilateral triangles c) Use 7 matches to make 3 equilateral triangles d) Use 12 matches to make 6 equilateral triangles *Note: A match can be used as a common side between two triangles Extension activities (if time): 1. Using 15 matches: a) Construct as many different isosceles triangles as you can. Draw your solutions, clearly showing the number of matches used on each side of each triangle. b) Construct as many different scalene triangles as you can. Draw your solutions, clearly showing the number of matches used 2. Using 6 matches, construct four equilateral triangles. All triangles must have side lengths of one match. Answers: Triangles 1. Complete the table. Keep completed table for your own reference. Picture Name of Triangle Definition Isosceles Triangle Two equal sides; Two equal angles Equilateral Triangle All sides equal; All angles equal Obtuse-angled triangle One angle is greater than 90° Right-angled triangle Has one right angle Scalene Triangle All sides different; All angles different Acute-angled triangle All angles are less than 90° Answers: 4. a) 4,4,4 b) 3,4,5 c) 5,5,2 5. a) b) c) c) Extension activities: 1. a) Three isosceles triangles: 4,4,7; 6,6,3; 7,7,1. b) Three scalene triangles: 2,6,7; 3,5,7; 4,5,6. 2. A tetrahedron (four triangular faces)