M3.5.6 For the adult
Line symmetry and reflection
In how many ways can I fold a rectangle so that both halves match?
What this chapter teaches
A line of symmetry cuts a shape into two halves that fold exactly onto each other. A reflection places every point the same distance from the mirror line on the other side. A regular polygon has one line of symmetry for each side.
Three questions to ask
There is no one right wording. Listen for the idea.
- How do you test whether a line is a line of symmetry?
- Why is the diagonal of a rectangle not a line of symmetry?
- A point is 3 squares left of a mirror line. Where is its image?
After the chapter, the learner can
- Find all the lines of symmetry of a shape
- Draw the reflection of a shape in a mirror line
What they copy into their notebook
A line of symmetry gives two halves that fold onto each other. A reflection puts every point the same distance from the mirror line on the other side. A regular polygon has as many lines of symmetry as sides.