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0:04   Hi, everyone! Today we're going to learn about symmetry.
0:10   Symmetry is a concept that is commonly found in math - especially geometry -
0:16  but it is also often discussed in art and design.
0:21  An object that has symmetry can be divided into identical pieces. When an
0:27  object has symmetry, we say that it is symmetrical. When an object does not
0:33  have symmetry, we say that it is asymmetrical.
0:39  There are many different types of geometric symmetry, but today we are only
0:43  going to talk about the simplest form, reflectional symmetry. An object or
0:50  image that has reflectional symmetry is like a mirror image.
0:56  If you were to draw an imaginary line down the center of a symmetrical object
1:00  and fold it in half along that line, the shapes would match up. This
1:06  imaginary line is called a 'line of symmetry.' Some symmetrical objects only
1:12  have one line of symmetry, while others have more.
1:18  For example, this triangle only has one line of symmetry, straight down the
1:24  middle, because if you try to divide it any other way the pieces don't match up.
1:31  This triangle, on the other hand, has three lines of symmetry. You could fold
1:37  it here, here, or here, and each time the halves would be the same.
1:46  A square has four lines of symmetry. You could divide it in half from left to
1:51  right, top to bottom, or from corner to corner either way.
1:59  Symmetry is often found in nature. One favorite example of this is a
2:09  butterfly. When a butterfly folds its wings, it is easy to see that they are
2:15  the same shape.
2:19  Now that you know what symmetry means, see if you can find symmetrical
2:24  objects near you. You may be surprised by how many things are symmetrical!

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