Linear algebra-how do I know if something is invertible?

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SUMMARY

The discussion centers on determining the invertibility of a linear transformation represented by a reflection about the line y = x/3 in R². It is established that a transformation T is invertible if its matrix representation is invertible. The participants confirm that reflections across a line through the origin are inherently invertible, as performing the reflection twice returns the original position. The vertical and horizontal line tests are mentioned as tools for assessing function properties, although their application to transformations is clarified as limited.

PREREQUISITES
  • Understanding of linear transformations and their matrix representations
  • Familiarity with the concept of invertibility in linear algebra
  • Knowledge of geometric interpretations of reflections in R²
  • Basic comprehension of the vertical and horizontal line tests
NEXT STEPS
  • Study the properties of linear transformations and their matrices
  • Learn about the geometric implications of reflections in linear algebra
  • Explore the concept of eigenvalues and eigenvectors for further insights on invertibility
  • Investigate the relationship between transformations and their inverses in R²
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Students of linear algebra, mathematicians, and educators seeking to deepen their understanding of invertible transformations and reflections in two-dimensional space.

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Linear algebra--how do I know if something is invertible?

Say I have a "reflection about the line y = x/3 in R^2," how do I know if the function or "T" is invertible?

Thank you.
 
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T is inv if its matrix is invertible, I think reflecting about y = x/3 function/T is invertible .

just use vertical/horizontal line test for functions
 
Well you could first find out what the matrix representation of this linear transformation is. Are you familiar with these terms?
 
yes, but how does the vertical line test work?
 
I don't think it would work on transformations >>

for functions draw a vertical line, if it passes through the function twice then that means your function is not an actual function

and for inverse, draw horizontal line ...

something really simple stupid that I never used
 
Well there is an invertible transformation for any reflection across a line through the origin.
 
Geometrically, if you reflect a second time across the same line, you are right back where you started. Any reflection is its own inverse.
 

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