What are similar triangles?

Similar triangles are triangles that have the same shape but might be different sizes, like two toy blocks that look alike, one smaller and one bigger.

Imagine you're building with blocks. You take a triangle block, and then you make another triangle block that’s exactly like it, just bigger or smaller. These are similar triangles, they match in angles and proportions, even if their sides aren’t the same length.

Like Copying a Picture

If you draw a triangle on a piece of paper and then use a magnifying glass to look at it, your eye sees a bigger version of that triangle. The original triangle and the one you see through the magnifying glass are similar triangles, they match in shape but not size.

Like Stretching a Rubber Band

Think about stretching a rubber band into a triangle shape. If you stretch it more, it becomes a bigger triangle. If you let it relax, it goes back to its original size. Both triangles, the stretched one and the relaxed one, are similar triangles because they look alike even when one is bigger or smaller.

They’re like friends who wear the same kind of clothes but different sizes, still matchy-matchy!

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Examples

  1. Two triangles on a pizza that look like they could be cut from the same pie
  2. A small model car and its real-life version, both with matching angles
  3. Two trees casting shadows at the same time of day

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Categories: Art · geometry· triangles· similarity