Why is square root not following square properties?

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Jamie
Jamie 2014-7-11
评论： Jamie 2014-7-11
Hello,
When I run this segment of code. The two different ways of writing the square roots don't equal (this can obviously vary with the random values in matrix "a").
a = rand(4);
sqrt(5)./sqrt(a)==sqrt(5./a)
ans =
0 1 0 1
1 0 0 0
0 1 0 1
1 0 1 1
As far as I know, this property of square roots should be valid, however it seems to not be giving an answer consistent with my understanding.
Any help would be greatly appreciated

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Image Analyst
Image Analyst 2014-7-11
I think because they're computed in different ways, the expressions on each side are different from each other way out in the 7th or 8th decimal place. To understand this you should read the FAQ: http://matlab.wikia.com/wiki/FAQ#Why_is_0.3_-_0.2_-_0.1_.28or_similar.29_not_equal_to_zero.3F Some of them might match exactly and those locations give a 1 but where they don't exactly match all the way out to the last decimal place, those locations will be a 0, indicating "no equality".

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