# Who decided, and when , that a right angle was 90 degrees ?

**URL:** https://boards.straightdope.com/t/who-decided-and-when-that-a-right-angle-was-90-degrees/648839
**Category:** Factual Questions
**Created:** [January 30, 2013, 10:00pm UTC](https://boards.straightdope.com/t/who-decided-and-when-that-a-right-angle-was-90-degrees/648839 "2013-01-30T22:00:24Z")
**Posts on this page:** 4
**Page:** 3

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### Author: ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)
#### Post date: [January 31, 2013, 4:57pm UTC](https://boards.straightdope.com/t/who-decided-and-when-that-a-right-angle-was-90-degrees/648839/41 "2013-01-31T16:57:01Z")

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> [@President\_Johnny\_Gentle](#):
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> I’ve entertained my calc students in the past by computing exponentials for small values of x in my head. They tend to be impressed until they start picking out the easy trick.

My algebra teacher in high school used to say, “first one to get this next problem right doesn’t have to come to school tomorrow!”

It took us a really long time before we realized he only made this offer on Fridays.

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### Author: ![Darth\_Panda](https://avatars.discourse-cdn.com/v4/letter/d/ee7513/32.png) [@Darth\_Panda](https://boards.straightdope.com/u/Darth_Panda)
#### Post date: [January 31, 2013, 5:16pm UTC](https://boards.straightdope.com/t/who-decided-and-when-that-a-right-angle-was-90-degrees/648839/42 "2013-01-31T17:16:12Z")

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> [@Kobal2](#):
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> The question is nonsense, NONSENSE ! A right angle isn’t 90°. It’s π/2 radians.

Maybe if you’re a communist. I won’t be splitting my pi with anyone. All of those radians are mine damnit!

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### Author: ![dropzone](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dropzone/32/7515_2.png) [@dropzone](https://boards.straightdope.com/u/dropzone)
#### Post date: [February 1, 2013, 12:48am UTC](https://boards.straightdope.com/t/who-decided-and-when-that-a-right-angle-was-90-degrees/648839/43 "2013-02-01T00:48:41Z")

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> [@Senegoid](#):
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> Would you like to know if 0.999… = 1 (and if so, why)? 🆒

Nope. Figured that one out without Cecils help: “It just is. Think about it. Now think about some more. See?”

Cuz damned if it ain’t.

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### Author: ![Chefguy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chefguy/32/138_2.png) [@Chefguy](https://boards.straightdope.com/u/Chefguy)
#### Post date: [February 1, 2013, 3:32pm UTC](https://boards.straightdope.com/t/who-decided-and-when-that-a-right-angle-was-90-degrees/648839/44 "2013-02-01T15:32:12Z")

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> [@Malacandra](#):
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> Plus which, when you’re using radians and e, there’s a simple equation unifying e, i, p, 0 and 1.

Is this how mathematicians sing “Old McDonald”?

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