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Transformations & Symmetry  Lesson 16
Today, we went over a lot of notes! We started with the following warmup:
Hopefully, you can find the measure of the angle to be 90°!
We then started the lesson...we started by defining a rigid transformation and showing an example:
Next, we talked about a nonrigid transformation and showed an example...something called a dilation.
At this point, I told you that we would only be studying rigid transformations this year! Of these, there are three types you'll need to know: translations, rotations, and reflections. We started by defining a translation:
Next, we moved to defining rotations. For these, we noted a few things we needed to know:
We then discussed reflections. For these, we needed a preimage and a line over which we could reflect!
Next, I showed you how two reflections, over intersecting lines, give the same result as a rotation! Can you determine the degree the preimage was rotated to form the image here? (It's 117°)
Next, we talked about some special rules that you can use when performing some transformations on the coordinate plane:
The other rules, in case you were wondering, are (x, y)>(x, y) for 180° rotation, (x, y)>(y, x) for 270° rotation and (x, y)>(y, x) for a reflection across the line y = x.
At this point, we discussed different types of symmetry...starting with line symmetry:
We FINALLY wrapped up by discussing rotational symmetry:
Notice that the first example above has 120° rotational symmetry and the second example has point symmetry (180° rotational symmetry).
Whew! That was a lot for one day!
