Isosceles Right Triangle Formula Doesn't Work...

cjcrank

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Aug 31, 2012
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2
Hello,
There are several places on the internet that state if you know the hypotenuse you can figure out the length of the other 2 equal legs of an Isosceles Right Triangle.
The formula looks like this:

x^2 + x^2 = c^2
Since both of the legs are equal in length you can call both legs x.

I'm putting a diagonal brace between a beam and post on my deck and wanted to measure down the post and across the beam the same amount to center the brace. The brace is 39.25" long so the formula should be this;

x^2 + x^2 = 6.26^2
2x^2 = 39.25
x^2 = 19.63
x = 4.43

This all looks good on paper until you apply it in the real world with a tape measure.
When you square 4.43 (19.62(leg a)) and square leg b (19.62) and add them together you get - surprise - 39.25.
However! when you center the brace on the beam and post, each leg a and leg b = 28" not 19.62!

In reality x = 5.29^2 not 4.43^2 which when applied to the formula, the hypotenuse would be 56"!

Am I missing something? I have found this formula in several places on the internet (is that my problem?)
Thanks
 
Is the brace a trapezoid, in which case you might be measuring the long side instead of the short side.
 
x^2 + x^2 = c^2

I thought 39.25 WAS c squared so I took the square root of 39.25 for c (6.26).
When you square 39.25 and put it in the formula it works.
Thanks for the help guys!
 
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