Similar figures (8th grade math)

In simple terms, two figures are similar figures if they have the same basic shape (but are not necessarily the same size). Mathematically speaking, two figures are similar if there is a sequence of transformations mapping one to the other (reflections, translations, rotations, and dilations are allowed).

We also look at an exercise where a triangle is mapped to another, using a sequence of transformations, proving they are similar. Then in another exercise, we're given the coordinates of the vertices for two distinct transformations, and the task is to figure out what transformations they were.

Similar figures, part 2

When two geometric figures are similar, they have the same basic shape but are not necessarily the same size. We multiply the side lengths of one by the scale factor to get the side lengths of the other. One can also use a scale ratio. I explain how to get the scale ratio from the scale factor. To calculate unknown side lengths, we can use the scale factor, or set up a proportion.

See also

Translations and reflections — video lesson

Practice geometric transformations online

Math Mammoth Grade 8 curriculum

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