Lines of symmetry
Complete a simple symmetric figure with respect to a specific line of symmetry
What a learner can do afterwards
- Given half a butterfly shape and a mirror line, complete the other half on a grid
- Complete a symmetric pattern on squared paper with a vertical line of symmetry
- Check a completed figure by folding along the mirror line
The lesson
A line of symmetry is a mirror line. If you fold a shape along this line, both halves land exactly on top of each other. You already know how shapes look and how they move on a grid. Now you will use that grid to finish a shape when you only see half of it.
Zara sees half a butterfly wing drawn on squared paper, with a mirror line down the middle. For every square she counts on one side, she counts the same square on the other side, the same distance from the line. She marks a dot there, then joins the dots to finish the wing.
To check your work, fold your paper along the mirror line. If the two halves match up exactly, your drawing is symmetrical. If a part sticks out, fix that part.
A line of symmetry is a mirror line: copy each square the same distance on the other side, then fold to check.
Watch it
Where it sits
Learn first
This opens up
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.