Basics of Symmetry

In this lesson, we will learn:

• How to identify symmetrical vs. asymmetrical shapes or pictures
• How to check symmetry lines with the folding method or mirror test method

Notes:

• A "symmetrical" shape is made up of exact same parts facing each other
• A line of symmetry divides a symmetrical shape into 2 congruent parts
• If the shape is not symmetrical it is "asymmetrical"

• Check if a shape has a line of symmetry by folding it in half to see if the parts match up

• or using a mirror test: laying the picture/shape flat and putting a mirror on a possible symmetry line to see if the mirrored image matches with the original

• Some shapes have more than one line of symmetry. Regular polygons have the same number of symmetry lines as number of sides

Ex. triangles = 3 sides = 3 symmetry lines
• some words (alphabet letters) and numbers also have symmetry: