Reflecting triangle points

Reflecting triangle points

Pencil and paperOnline interactive
Overview
Using this Resource
Connecting to the Curriculum
Marking Student Responses
Working with Students
Further Resources
This task is about lines of symmetry.
 
Use the diagram below to help answer the following questions.
labelled triangle

Question 2Change answer

a)  If the triangle ABE was reflected on to triangle AJG, what would the line of symmetry be? 

Question 2Change answer

b)  Complete this statement.
     Triangle BDC reflects on to triangle in the line BD.

Question 2Change answer

c)  Name four different pairs of triangles which reflect on to each other in the line of symmetry AF.   
     i)   Triangle reflects onto triangle in the line AF.

     ii)  Triangle reflects onto triangle in the line AF.

     iii) Triangle reflects onto triangle in the line AF.

     iv) Triangle reflects onto triangle in the line AF.
Task administration: 
This task can be completed with pen and paper or online (with NO auto marking).
Level:
5
Curriculum info: 
Maths, Geometry and Measurement, Shape, Transformation
Keywords: 
symmetry, reflection, transformations, lines, line segments, triangles
Description of task: 
In a shape made up of triangles, students identify lines of symmetry for pairs of triangles and identify pairs of triangles which reflect through a line of symmetry.
Learning Progression Frameworks
This resource can provide evidence of learning associated with
Geometric thinking, set 6
within the Mathematics Learning Progressions Frameworks.
Read more about the Learning Progressions Frameworks.
Answers/responses: 
  Y10 (09/1998)
a) Line AF (or FA). easy
b) BDE (letters in any order). easy
c) Any 4 of:

ABE, AJG
BDE, JHG
ACE, AIG
CBE, GJI
AFE, AFG
ACG, AIE
AFC, AFI
BCD, JHI
NOTE:  Pairs can be written either way around, and letters in any order.

 4 correct – moderate

2-3 correct – very easy

 

Diagnostic and formative information: 
  Common error Likely reason
c) BDC, BDE
GHJ, IHJ		 Reflects in BD rather than AF
Reflects in HJ rather than AF
Next steps: 
Extension 
Find all pairs of triangles which reflect on to each other in the line of symmetry AF.
Ask how students know these are all the pairs (justify).