Why do linear algebra books have this cover? [closed]

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From the preface of Matrix Analysis:

"The cover art for the second edition was the result of a lucky encounter on a Deltaflight from Salt Lake City to Los Angeles in spring 2003. The young man in themiddle seat said he was an artist who paints abstract paintings that are sometimesmathematically inspired. In the course of friendly conversation, he revealed that hisspecial area of mathematical enjoyment was linear algebra, and that he had studiedMatrix Analysis. After mutual expressions of surprise at the chance nature of ourmeeting, and a pleasant discussion, we agreed that appropriate cover art would enhancethe visual appeal of the second edition; he said he would send something to consider.In due course a packet arrived from Seattle. It contained a letter and a stunning 4.5- by5-inch color photograph, identified on the back as an image of a 72- by 66-inch oil oncanvas, painted in 2002. The letter said that “the painting is entitledSurprised Againon the Diagonaland is inspired by the recurring prevalence of the diagonal in mathwhether it be in geometry, analysis, algebra, set theory or logic. "

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