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Reference.org
Identity matrix
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<p>In <a href="/facts/Linear_algebra/8VaB4VWk">linear algebra</a>, the identity matrix of size n {\displaystyle n} is the n × n {\displaystyle n\times n} <a href="/facts/Square_matrix/5TP9mNNn">square matrix</a> with <a href="/facts/One/m3wpSfMf">ones</a> on the <a href="/facts/Main_diagonal/rkT2F08Q">main diagonal</a> and <a href="/facts/Zero/4NBRtKHc">zeros</a> elsewhere. It has unique properties, for example when the identity matrix represents a <a href="/facts/Geometric_transformation/qRjrasJf">geometric transformation</a>, the object remains unchanged by the transformation. In other contexts, it is analogous to multiplying by the number 1. </p>