alright just for fun: AMA but only about math, will attempt to speed-explain stuff with as few symbols and equations as possible and see what happens
(esp happy to field questions about stuff that seems basic to you and that you feel like you should've gotten a long time ago!)
Conversation
I hit my head and had a weird dream where the condition number of a matrix was only norm(A)*norm(A^-1), but I have seen lately being written as the ratio of the max/min eigenvalues of A. What’s the truth and how on earth are those 2 equivalent? I can’t derive one from the other
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norm(A) is the largest singular value of A, which agrees with the largest eigenvalue if A is symmetric but not in general. the eigenvalue definition is wrong if A isn't symmetric imo