$\sqrt{(-1)^2}$: Is it -1 or 1?

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SUMMARY

The discussion centers on the evaluation of the expression $\sqrt{(-1)^2}$. Two interpretations are presented: the first interpretation leads to the conclusion that $\sqrt{(-1)^2} = -1$ through the product property of radicals, while the second interpretation simplifies it to $\sqrt{1} = 1$. The key takeaway is that the product property of radicals only holds when both factors are non-negative, which is crucial for determining the correct outcome in this context.

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footmath
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Is it correct ?
$ \sqrt{(-1)^2} $ = $ \sqrt{(-1)}\sqrt{(-1)} $= $ i*i $=$ i^2 $ =$ -1 $
or
$ \sqrt{(-1)^2} $ = $ \sqrt{(1)} $=1
 
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You mean this?
[itex]\text{1) }\sqrt{(-1)^2} = \sqrt{(-1)} \cdot \sqrt{(-1)} = i \cdot i = i^2 = -1[/itex]
[itex]\text{2) }\sqrt{(-1)^2} = \sqrt{1} = 1[/itex]

Note that the product property of radicals,
[itex]\sqrt{ab} = \sqrt{a} \cdot \sqrt{b}[/itex]
holds only if both a and b are non-negative.
 

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