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 Dec20 awarded Constituent Dec16 awarded Caucus Oct27 comment open interval written as countable union of closed intervals Formal verification relies on the Archimedean property of $\mathbb{R}$. Oct14 comment Notation: subscript vs. superscript for coordinate vector fields Hi, IMO the video is saying there are two ways to extract meaningful coordinates in an oblique coordinate system: taking orthogonal projection to oblique axes gives a covariant vector; parallel projections gives a contravariant vector. Neither is wrong or right by itself. The key is that inner product of covariant and contravariant gives an invariant independent of obliqueness of coordinate system. This invariant is exactly norm-squared when in orthogonal coordinates where covariant = contravariant. So both projections are part of understanding length. Does that help? @EricAuld Oct14 comment Gauss Disq. Arithm. Translation Errata? +1 A bold project -- well done! Oct1 awarded Yearling Sep30 awarded Explainer Sep24 awarded Autobiographer Sep22 revised Notation: subscript vs. superscript for coordinate vector fields Added reference Sep22 suggested rejected edit on Matrix rows notation Aug12 revised Notation: subscript vs. superscript for coordinate vector fields Put picture before explanation. Aug12 answered Notation: subscript vs. superscript for coordinate vector fields Aug11 revised Notation: subscript vs. superscript for coordinate vector fields Revised the phrasing to avoid ambiguity by putting the descriptor before each example. Aug11 suggested approved edit on Notation: subscript vs. superscript for coordinate vector fields Aug11 comment Parenthesis vs brackets for matrices No, ll ll is a notation usually reserved for the norm of a matrix. Jul7 revised Keep getting generating function wrong (making change for a dollar) Added the actual problem into title so it surfaces when searching for making change. Jul7 suggested approved edit on Keep getting generating function wrong (making change for a dollar) Jul7 comment Making Change for a Dollar (and other number partitioning problems) Worth noting that the list of available denominations in this version includes the non-change making option of \$1.00. The solution is of course 292 for the usual version with strictly smaller denominations up to 50c (George Polya in How To Solve It, 1971). Jul7 comment Making Change for a Dollar (and other number partitioning problems) (+1) Very interesting references. Jul3 revised How do I read this question? (subject: bijections) OP had acknowledge AKE. AKE's handle has changed to Assad Ebrahim. Updated the reference.