Linear algebra involving dot product and orthongal matrices

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SUMMARY

The discussion centers on proving that the norm of a vector transformed by an orthogonal matrix remains unchanged, specifically showing that ||Rx|| = ||x|| for a vector x in R^n and an orthogonal matrix R. The key property of orthogonal matrices is highlighted: R^TR = RR^T = I, where I is the identity matrix. This property is essential in demonstrating that the transformation preserves the length of the vector.

PREREQUISITES
  • Understanding of vector operations, specifically the dot product and transpose.
  • Familiarity with orthogonal matrices and their properties.
  • Knowledge of vector norms and their geometric interpretations.
  • Basic linear algebra concepts, particularly in R^n.
NEXT STEPS
  • Study the properties of orthogonal matrices in detail, focusing on their role in linear transformations.
  • Learn about vector norms and how they relate to inner products in linear algebra.
  • Explore the implications of the identity matrix in transformations and its significance in preserving vector lengths.
  • Investigate applications of orthogonal matrices in various fields, such as computer graphics and machine learning.
USEFUL FOR

Students and professionals in mathematics, particularly those studying linear algebra, as well as anyone involved in fields requiring an understanding of vector transformations and orthogonal matrices.

ItsKP
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Homework Statement


Given: x (dot) y = x^T * y (where x,y are vectors; dot is dot product; and x^T is x transpose)
and R is an orthogonal nxn matrix, and x,y are elements of R^n

Show ||Rx|| = ||x||


The Attempt at a Solution



I'm not sure what information I am suppose to use to solve this. This is what I have gathered so far:
x(dot)y = x1y1 + x2y2+ ... + xnyn = x^T * y

But how am I suppose to use any of this to solve the problem? Is it involving inner products at all?
 
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ItsKP said:

I'm not sure what information I am suppose to use to solve this.


The crucial information is that R is an orthogonal matrix: R^TR=RR^T=Identity matrix.
 

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