# triangle puzzle

**URL:** <https://boards.straightdope.com/t/triangle-puzzle/108373>\
**Category:** Factual Questions\
**Created:** [May 10, 2002, 9:22pm UTC](https://boards.straightdope.com/t/triangle-puzzle/108373 "2002-05-10T21:22:19Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![nick112](https://avatars.discourse-cdn.com/v4/letter/n/ecc23a/32.png) [@nick112](https://boards.straightdope.com/u/nick112)\
**Post date:** [May 10, 2002, 9:22pm UTC](https://boards.straightdope.com/t/triangle-puzzle/108373/1 "2002-05-10T21:22:19Z")

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Could someone please explain this to me?

[http://www.ebaumsworld.com/trigrid.html](http://www.ebaumsworld.com/trigrid.html)

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**Author:** ![elfoldo](https://avatars.discourse-cdn.com/v4/letter/e/e47c2d/32.png) [@elfoldo](https://boards.straightdope.com/u/elfoldo)\
**Post date:** [May 10, 2002, 9:55pm UTC](https://boards.straightdope.com/t/triangle-puzzle/108373/2 "2002-05-10T21:55:27Z")

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My guess is that it’s an optical illusion.

I don’t think the diagonal of the triangles are exactly the same. It looks like the one on the bottom is slightly higher than the one on the top. See where the diagonal crosses each grid axis and you’ll see that the one on the bottom is slightly higher than the one on the top. I’m guessing that the triangle on the bottom has slightly more area than the one on the top (exactly 1 square bigger).

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**Author:** ![iamthewalrus\_3](https://avatars.discourse-cdn.com/v4/letter/i/258eb7/32.png) [@iamthewalrus\_3](https://boards.straightdope.com/u/iamthewalrus_3)\
**Post date:** [May 10, 2002, 9:56pm UTC](https://boards.straightdope.com/t/triangle-puzzle/108373/3 "2002-05-10T21:56:29Z")

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This has been answered many times before. Simply, it’s not a triangle. The top one is slightly concave. The bottom, slightly convex. The lines are thick enough to hide minor changes.

To see why, measure the side length ratios for the two internal “triangles” and for the big “triangle.”

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**Author:** ![iamthewalrus\_3](https://avatars.discourse-cdn.com/v4/letter/i/258eb7/32.png) [@iamthewalrus\_3](https://boards.straightdope.com/u/iamthewalrus_3)\
**Post date:** [May 10, 2002, 10:00pm UTC](https://boards.straightdope.com/t/triangle-puzzle/108373/4 "2002-05-10T22:00:04Z")

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So… I just checked the site again.

Tell me, did you try clicking on the link that says: “Click here to see peoples explanations here!”?

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**Author:** ![nick112](https://avatars.discourse-cdn.com/v4/letter/n/ecc23a/32.png) [@nick112](https://boards.straightdope.com/u/nick112)\
**Post date:** [May 10, 2002, 10:50pm UTC](https://boards.straightdope.com/t/triangle-puzzle/108373/5 "2002-05-10T22:50:59Z")

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Ok, i was looking at it again, and you are right. They r not triangles. Just using simple trig, using Tan (opposite/adjacent) the green triangle comes to Tan=.4, and the red triangle comes to Tan=.375. The angles of the green and red triangle should be equal. Also, the tan of the green and red should be equal to the tan of the Large triangle which is around .38. The triangles are not triangles at all, but 2 straight sides and one curved side.

Thank you for your help.