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With the linear maps $T_1$ and $T_2$ be linear endomorphisms on a vector space $V$. If $T_2$ is diagonalizable, is $T_1$$(T_2)$ also diagonalizable? Also if $f(T)$ = $T_1(T_2)$ is $f$ diagonalizable? How do I show this is the case?

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What if $T_1$ is not diagonalizable, and $T_2$ is the identity map?

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    How would $T_2$ being identity map make the composition diagonalizable?2017-02-23
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    @BBest That’s exactly the point.2017-02-23
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    @amd but wouldn't $T_2$ map all **v** to itself? Then I don't understand how that has an effect of diagonalizablilty for $T_1$2017-02-23
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    @BBest In your question, you didn’t ask about the diagonalizability of $T_1$. You asked about the diagonalizability of the composition of the two maps.2017-02-23
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    Right, I guess I should of more specifically asked how do I show this2017-02-23
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    @B Best: My answer shows that it's possible to have $T2$ diagonalizable, but $T1(T2)$ _not_ diagonalizable.2017-02-23