Is T a One-to-One Linear Operator?

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SUMMARY

In the discussion, it is established that if T is a linear operator on a finite-dimensional vector space V and satisfies the condition ||T(x)|| = ||x|| for all x in V, then T is a one-to-one operator. The proof involves showing that if T(x) = T(y), then it must follow that x = y. The discussion also highlights the utility of the theorem that states \ker(T) = {0} as a more straightforward approach to demonstrate the one-to-one nature of T.

PREREQUISITES
  • Understanding of linear operators in vector spaces
  • Familiarity with norms and inner products
  • Knowledge of finite-dimensional vector spaces
  • Concept of kernel of a linear operator
NEXT STEPS
  • Study the properties of linear operators in finite-dimensional spaces
  • Learn about the relationship between norms and inner products
  • Explore the implications of the kernel of a linear operator
  • Investigate proof techniques such as proof by contradiction
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This discussion is beneficial for mathematics students, particularly those studying linear algebra, as well as educators and anyone interested in the properties of linear operators and their applications in vector spaces.

H12504106
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Homework Statement



Let T be a linear operator on a finite dimensional vector space V. Suppose ||T(x)|| = ||x|| for all x in V, prove that T is one to one.

Homework Equations



||T(x)||^2 = <T(x),T(x)>
||x||^2 = <x,x>

The Attempt at a Solution



Suppose T(x) = T(y) x, y in V
Then ||T(x)|| = ||T(y)||
and so <T(x),T(x)> = <T(y),T(y)>
By assumption, we have <x,x> = <y,y>
But then i can't proceed on to show that x=y
 
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H12504106 said:

Homework Statement



Let T be a linear operator on a finite dimensional vector space V. Suppose ||T(x)|| = ||x|| for all x in V, prove that T is one to one.

Homework Equations



||T(x)||^2 = <T(x),T(x)>
||x||^2 = <x,x>

The Attempt at a Solution



Suppose T(x) = T(y) x, y in V
Then ||T(x)|| = ||T(y)||
and so <T(x),T(x)> = <T(y),T(y)>
By assumption, we have <x,x> = <y,y>
But then i can't proceed on to show that x=y
One form of the definition for one-to-one is this:
For all x and y in V, T(x) = T(y) ==> x = y.
You can do a proof by contradiction by assuming that for some x and y in V, T(x) = T(y) and x [itex]\neq[/itex] y.

You need to use the fact that T is a linear operator.
 
If you've seen the right theorem, proving that [itex]\ker(T) = \{0\}[/itex] might be a slightly easier way to do this.
 

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