Mark Eichenlaub
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 Mar25 asked What are the 2125922464947725402112000 symmetries of a Rubik's Cube? Mar20 revised Logic question: Ant walking a cube deleted 11 characters in body Mar20 answered Logic question: Ant walking a cube Mar17 accepted What am I doing when I separate the variables of a differential equation? Mar16 awarded Nice Question Mar16 comment What am I doing when I separate the variables of a differential equation? Thanks for the link, but the description there is not what you said. Differentials as described in Wikipedia are not infinitesimal changes. Mar16 comment What am I doing when I separate the variables of a differential equation? The $dx$ and $dy$ are coming from a single limit. That's what I've been taught in calculus. This answer is logically equivalent to saying "you can do that because you can do that". Mar16 asked What am I doing when I separate the variables of a differential equation? Mar14 comment What is an intuitive explanation for $\operatorname{div} \operatorname{curl} F = 0$? Why the down votes? Mar14 revised What is an intuitive explanation for $\operatorname{div} \operatorname{curl} F = 0$? added 87 characters in body Mar14 revised What is an intuitive explanation for $\operatorname{div} \operatorname{curl} F = 0$? added 5 characters in body Mar14 comment What is an intuitive explanation for $\operatorname{div} \operatorname{curl} F = 0$? @Billare Thanks. Should say "I'll use Gauss's..." Mar14 comment What is an intuitive explanation for $\operatorname{div} \operatorname{curl} F = 0$? @kake Right. It's not supposed to be a proof so much as a heuristic to suggest the identity might be true. Mar14 answered Non-traditional math concepts for early education Mar14 answered What is an intuitive explanation for $\operatorname{div} \operatorname{curl} F = 0$? Mar14 comment What is an intuitive explanation for $\operatorname{div} \operatorname{curl} F = 0$? I like the analogy to a fluid flow, but for the divergence, were you referring to many needles converging to or diverging from a point rather than one needle? That would make more sense to me since one needle cannot change its shape or grow and shrink. I'm also wary of considering a two-dimensional fluid when the curl is defined in three. Mar12 awarded Nice Question Mar11 comment Find maximum divisors of a number in range @Chan Think of the constraint as a surface in some high-dimensional space. You want to find the spot on the surface where some function is maximized. Then the directional derivative of the function along the surface must be zero in all directions of the surface. The directional derivative is the dot product of the gradient with the tangent to the surface, so the gradient of the function must be normal to the surface. The gradient of the constraint function is also normal to the surface, so these two gradients must differ by only a constant multiplier, called the Lagrange multiplier. Mar11 answered Find maximum divisors of a number in range Mar10 awarded Teacher