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Why not just define AA^T as A^2 for matrices?
ivgiz
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Title. The construction where a matrix A is, basically, squared by multiplying by its transpose is commonly used, but the construction obscures the similarity to squaring for single numbers.
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ivgiz
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rule 1: specifically wondering about the connection between algebra and linear algebra/algebra for matrices. to what extent does it make sense to extend algebra to operations on sets of numbers?
UnileverFR
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Cause it would be a huge pain in the ass. For example then A^(-1)A² wouldn't be A. Also what would A³ be? General integer powers of matrices are common.
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This question makes no sense to me. The transpose has a specific definition, and so does matrix multiplication. In general, AA^(T) ≠ A^(2). What does it even mean to "define" AA^(T) as A^(2)?
PearsonItalia
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Because AA^T and A^2 aren't always equal to each other.
In fact, A^2 may not even be defined when AA^T is.
If A is a 2x3 matrix, then AA^T will be a 2x2 matrix, but A^2 can't be computed, because you can't multiply a 2x3 matrix by itself.
CoraCarmack
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Because they are different. Not sure what you mean exactly
nhk_anime100
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Let A be a MxN matrix. B=A^T A is a MxM matrix while C=A A^T is a NxN matrix.
A^2 is commutative so A^2 = A^T A = A A^T, which means B=C.
andreykovatchev
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