Questions tagged [symmetry]

Questions about symmetry, in group theory, geometry or elsewhere in mathematics. See https://en.wikipedia.org/wiki/Symmetry

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Several symmetry formulas?

I have lost the book of my math course one day before the test. I want to review several formulas, but I haven't found them anywhere online. The formulas I am looking for are: Symmetry of a line with respect to a point Symmetry of a line with…
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Definition of symmetry

Let $X \subseteq R^2$. A symmetry of $X$ is isometry $f: R^2 \to R^2$ such that $f(X) = X$. For example, square has $8$ symmetries one of which is $R_{90}(a, b) = (-b, a)$. Is an element of $X$ is both an image and pre-image of a symmetry? So,…
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