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Feb
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comment Definition of “well defined” in mathematics
A naive definition of square root that is not well-defined: let $x \in \mathbb{R}$ be non-negative. We call $y \in \mathbb{R}$ the square root of $x$ if $y^2 = x$, and we denote it $\sqrt x$. This is ill-defined because there are two such $y$, and so we have not actually defined the square root.
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Jan
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answered Why does an argument similiar to 0.999…=1 show 999…=-1?
Jan
19
reviewed Looks OK marginal probability density function for variables with uneven range
Jan
15
answered Are all group homorphisms of the reals also linear transformations?
Jan
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awarded  Yearling
Dec
16
reviewed Looks OK What is the largest abelian subgroup in $S_n$?
Dec
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reviewed Leave Open Representations Verse Solution Concepts
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reviewed Close Plot the partial sums of a series - Matlab.
Dec
16
reviewed Leave Open In $S_5$, we have $aba^{-1}=b^2$, $b=(12345)$, find $a$.
Dec
16
reviewed Looks OK Liouville's Theorem Derivative solving?
Dec
16
reviewed No Action Needed Kernel of powers of a normal operator
Dec
16
reviewed Leave Open Small Sample size Confidence Intervals
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reviewed Leave Open Isomorphism of Galois groups of the intersection
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16
reviewed Leave Open Continuum hypothesis outside of ZFC
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16
reviewed Leave Open What's the general mathematical method to go about solving a substitution cipher?
Dec
15
reviewed Leave Open Find transitive relations
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15
reviewed Close Question on circles geometry
Dec
15
reviewed Leave Open How is $e^x$ read aloud?