# V. Quick Matrix question

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Is a zero matrix the same thing as an identity matrix?

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The zero matrix is all zeros, and any matrix multiplied with it results in the zero matrix. For a square matrix, I (identity) is all zeros except for the major diagonal entries which are all 1. A matrix multiplied by I is unchanged. So:

0*M = M*0 = 0

I*M = M*I = M

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aah I see, so multiplying a matrix by a zero matrix turns that matrix into a 0 matrix , whereas multiplying it by an identity matrix doesnt change it... duh.. :)

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Yeah.

Also, a zero matrix looks like:

[0 0 0 ...]
[0 0 0 ...]
[... ]

An identity matrix looks like:

[1 0 0 ...]
[0 1 0 ...]
[0 0 1 ...]
[....... 1]

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