Although over there are plenty of kinds of symmetry, primary school school typically presents just reflective the opposite (or “mirror symmetry”). As a result, school materials tend come use words symmetry together if it had only that one meaning. This post will focus on the one meaning, however illustrate others as well.

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This picture shows a basic picture with a mirror placed along the line of symmetry. The an outcome that one watch — fifty percent of the original and the mirror image of that half — exactly matches the initial figure. We say the the original figure is “symmetric” through respect to the mirror; it has actually reflective symmetry.

## Reflective symmetry and also “line of symmetry”

Mirror-symmetric objects have at least one **line of symmetry**, a line follow me which the figure can be folded into two precisely equivalent parts, parts that space mirror images of each other.

This figure has 2 lines the symmetry: the horizontal line of symmetry cut the figure into a top and bottom that room mirror images of every other; the vertical line of symmetry cut the number into a left and right that room mirror pictures of each other. The star below has 5 lines of symmetry, 5 lines on which it have the right to be urgently so the both sides complement perfectly.

**A common misconception** uncovered even in plenty of glossaries and also texts: no all lines that division a figure into 2 congruent parts are present of symmetry. Because that example, the diagonal of a (non-square) rectangle is not a line of symmetry.

When a mirror is placed along the diagonal line of a rectangle, the result does no look the same as the original rectangle, for this reason the diagonal line is no a line of symmetry. This new shape — the combination of the triangular fifty percent of the original rectangle and also its image in the mirror — is dubbed a kite.

## Mirror Play

Well prior to children begin any type of formal research of symmetry, playing v mirrors — perhaps on pattern Block designs the they build — develops experience and also intuition that can serve both their geometric thinking and also their imaginative ideas. The colorful design above has just vertical and horizontal present of symmetry, but placing a winter on that at one more angle can produce a beautiful new design.

The very first figure below shows that the letter A has a vertical heat of symmetry, yet it’s quite “tame” play. An ext intrepid experiments provide other interesting results.The same is true of the letter M.

Letters like B and also D have actually a horizontal heat of symmetry: your top and also bottom parts match.

Some letters, because that example, X, H, and also O, have both vertical and also horizontal lines of symmetry.

And some, choose P, R, and also N, have no present of symmetry.

## Rotational symmetry

Another symmetry that kids sometimes usage in their Pattern Block design is “Rotational Symmetry.” A figure has rotational symmetry if part rotation (other 보다 a full 360° turn) produce the very same figure. For example, this figures, as soon as rotated just the appropriate amount — 360°/3 because that the “name” snapshot and 360°/5 because that the star — look exactly as lock did prior to rotation.

The letters, N, Z, and S likewise share that property.

Note that part figures, prefer the star and also the vivid blob in ~ the peak of the page, yet not the letters N, Z, or S, have actually both reflective and also rotational symmetry.

## The most symmetric shape

A circle has infinitely countless lines of symmetry: any type of diameter lies ~ above a heat of symmetry v the center of the circle. Any kind of rotation of any type of amount around the facility of the circle additionally leaves the one unchanged.

See more: What Does The Triangle With The Circle Inside Mean, What Does A Triangle Inside A Circle Mean

## Books because that children

For young children, K-2:Make a enlarge Puddle do a smaller Worm, through Marion WalterFor enlarge children, great 2 and also up:The winter Puzzle Book, by Marion Walter## What’s in a word?

The “metry” in symmetry and also geometry and metric refers to measurement.