In this module, you can study how to figure out whether triangles are similar; how to figure out side lengths in similar triangles.
The video above explains similar triangles in just three minutes. Toward the end, the tutor gives an example using "feet" as the unit of measure, but most of this video uses the metric system.
This video from Khan Academy goes into more detail about similar triangles.
You have to use measurements to tell whether two triangles are similar.
Two similar triangles can have different orientations on paper.
Practice and study
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similar triangles