# A particularly vexing illusion.
**URL:** https://boards.straightdope.com/t/a-particularly-vexing-illusion/241191
**Category:** Miscellaneous and Personal Stuff I Must Share
**Created:** [April 21, 2004, 7:35am UTC](https://boards.straightdope.com/t/a-particularly-vexing-illusion/241191 "2004-04-21T07:35:13Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@Baraqiyal](https://boards.straightdope.com/u/Baraqiyal)
#### Post date: [April 21, 2004, 7:35am UTC](https://boards.straightdope.com/t/a-particularly-vexing-illusion/241191/1 "2004-04-21T07:35:13Z")
[http://www.cs.memphis.edu/~mathewj/triangle.jpg](http://www.cs.memphis.edu/~mathewj/triangle.jpg)
Can you figure it out? This thing has been bothering me for days. I was about to post it to General Questions, but after giving it one last mental effort, I think I have it figured out.
I’ll post my solution tomorrow.
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### Author:  [@nikjohns](https://boards.straightdope.com/u/nikjohns)
#### Post date: [April 21, 2004, 7:43am UTC](https://boards.straightdope.com/t/a-particularly-vexing-illusion/241191/2 "2004-04-21T07:43:26Z")
From another message board: [http://apotheosis.tv/files/trigrid21.GIF](http://apotheosis.tv/files/trigrid21.GIF)
> [@](#):
>
> I should explain more. The bottom line makes the hypotenuse of the first “triangle” (not really a triangle) and the top line is the hypotenuse of the second “triangle.” The orange area is what makes the difference between the two, and it is the same as the area of one square.
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### Author:  [@Mangetout](https://boards.straightdope.com/u/Mangetout)
#### Post date: [April 21, 2004, 8:18am UTC](https://boards.straightdope.com/t/a-particularly-vexing-illusion/241191/3 "2004-04-21T08:18:58Z")
Offer up a straight edge to the longest ‘side’ of each ‘triangle’ and all will become clear.
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### Author:  [@Ogre](https://boards.straightdope.com/u/Ogre)
#### Post date: [April 21, 2004, 8:23am UTC](https://boards.straightdope.com/t/a-particularly-vexing-illusion/241191/4 "2004-04-21T08:23:49Z")
> [@Baraqiyal](#):
>
> [http://www.cs.memphis.edu/~mathewj/triangle.jpg](http://www.cs.memphis.edu/~mathewj/triangle.jpg)
>
> Can you figure it out? This thing has been bothering me for days. I was about to post it to General Questions, but after giving it one last mental effort, I think I have it figured out.
>
> I’ll post my solution tomorrow.
Our mysterious triangular figures, if I may be allowed to drop a hint, my not be triangles at all!
😉
And on preview, I see **Mangetout** hath beaten me to it. Crap.