Lines of Symmetry Flashcards

All 5 cards in this deck

What is a line of symmetry of a 2D shape?

A mirror line: folding the shape along it makes the two halves match exactly.

How many lines of symmetry does a regular polygon have?
e.g. a regular hexagon

The same number as its sides.
A regular hexagon has 6.

What are the steps to find all the lines of symmetry of a 2D shape?
e.g. a rectangle

1. Try each possible mirror line through the shape (through vertices or through midpoints of sides).
2. Check that folding along it makes both halves match exactly.
3. Count the lines that work: a rectangle has 2.

A shape has a line of symmetry. What does this tell you about the sides and angles on either side of that line?

Sides and angles that reflect onto each other are equal.

What are the steps to complete a shape so that a given line is a line of symmetry?
e.g. half a shape drawn to the left of a vertical mirror line

1. Measure each vertex's distance from the mirror line.
2. Mark a matching point the same distance on the other side (to the right).
3. Join the new points in the same order to complete the shape.