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Lines of Symmetry

Shape & Space · Year 2–Year 6

Shade squares and reflect them, or complete the pattern yourself.

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About the symmetry

An eight by eight grid with a mirror line through it. Tap a square and it shades, and with the mirror on its reflection shades too, so a class can see exactly where a square goes when it is reflected. Drag to shade a run of them.

Turn the mirror off and the tool stops helping. Shade half a pattern, hand the board over, and the class has to place the reflections themselves. The caption says how many squares are still missing, which is a fact rather than a score, and Complete fills them in when it is time to check.

Four mirror lines, not one: down the middle, across the middle and both diagonals. Changing the line does not clear the pattern, on purpose, because "is this pattern symmetrical about that line as well?" is the best question the tool can be asked, and a pattern that is symmetric about the vertical is very often not symmetric about a diagonal.

Symmetry here is about the shape rather than the colour: a reflection shaded in the wrong colour is still in the right place, and it is the shape the curriculum is asking about. The colours are for making a pattern worth looking at, and with the mirror on a reflection takes its partner's colour so a mirrored pattern really is mirrored.

How to use it on your whiteboard

  1. 1Tap a square to shade it, or drag to shade several. Tap it again to rub it out.
  2. 2Choose a mirror line: down the middle, across the middle, or either diagonal.
  3. 3Press Off under Reflect and shade half a pattern, then ask the class to finish it. The caption counts what is missing.
  4. 4Press Complete to fill in the missing squares, which is the check.
  5. 5Tap Fullscreen to fill the board. Clear empties the grid.

Questions

How do I set a pattern for the class to complete?
Shade half of one with the mirror on, then press Reflect Off and Clear one side by tapping those squares out. Or simply shade half a pattern with the mirror off from the start. The caption then counts what is missing without saying where.
Does the reflection have to be the same colour?
No. The check asks whether the mirror square is shaded, not what colour it is, because symmetry is about the shape. With the mirror on the reflection copies its partner's colour anyway, so a pattern built that way is mirrored in colour too.
Can a pattern be symmetrical about more than one line?
Yes, and finding out is the point of having four. Change the mirror line and the pattern stays where it is, so the same pattern can be checked against the vertical, the horizontal and both diagonals one after another.
Do I need an account?
No. Trove Tools is free with no login, no subscription and no limits.