M2.5.6 For the adult
Lines of symmetry
When do the two halves of a folded shape match?
What this chapter teaches
A line of symmetry is a fold where the two halves match exactly. A line through the middle does not always work. A diagonal of a rectangle that is not a square is a common wrong choice.
Three questions to ask
There is no one right wording. Listen for the idea.
- How can you test whether a line is a line of symmetry?
- How many lines of symmetry do you think a rectangle has, and where are they?
- Draw half a shape beside a mirror line. How will you draw the other half?
After the chapter, the learner can
- Find lines of symmetry by folding paper
- Complete a drawing so both sides of a mirror line match
What they copy into their notebook
A line of symmetry is a fold where the halves match. A square has 4. A rectangle has 2. A scalene triangle has 0. A diagonal of a rectangle fails.