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 Jan19 suggested approved edit on Which of these two ways to take the derivative of a delta function times another function is correct? Jan1 answered Finding an equation for a circle given its center and a point through which it passes Dec31 answered In this case, does $\{x_n\}$ converge given that $\{x_{2m}\}$ and $\{x_{2m+1}\}$ converge? Sep13 awarded Commentator Sep13 comment Is there any math operation defined to obtain vector $[4,3,2,1]$ from $[1,2,3,4]$? It's the called the reverse identity matrix J. J[1 2 3 4]^T = [4 3 2 1]^T. Sep10 answered What function is this? Jul21 comment Help with a derivative Just do it the normal way; or take the log of your expression and calculate its derivative. Jul20 comment What are the Axiom of Choice and Axiom of Determinacy? This answer is at the wrong level and self-indulgent. And honestly probably doesn't help the original poster. Jun18 comment Good textbooks on combinatorics for self-study I would not classify this book as introductory at all. Apr20 awarded Editor Apr20 revised Transformations of Normal added 47 characters in body Apr20 answered Transformations of Normal Apr14 comment Algorithmic Complexity of Iterated Sums I don't think so. Let f(a,n) := {if (n>1) n*f(a,n-1) else 1} = n!. Then f(a,n) is a polynomial-time algorithm using simple operations but F(n) is not a polynomial-time algorithm. Mar16 awarded Critic Mar16 comment Recommend a statistics fundamentals book If you just want a review, just read Schaum's Outline of Probability and Statistics. It's less than $16 new. Mar5 comment Explain$-\int^{a}_{b}\frac{Q}{4 \pi \epsilon \bar{r}^{2}} \cdot d \bar{r}= \left[\frac{Q}{4\pi \epsilon \bar{r}}\right]^{a}_{b}$In American textbooks, curl is usually written$\nabla \times\$. Mar5 answered More help with implicit differentiation Mar2 comment Line simplification algorithm Is the shape important or is only the frequency of the teeth important? If only the frequency of the teeth, you can use a color gradient instead. You have 5000 points but only 450 pixels, then split the line into fixed number intervals (each with 30 points for example) and calculate how many teeth there are in each interval. Then color code with red for very few teeth and blue for very many teeth. Feb28 comment Mathematical difference between white and black notes in a piano "harpsichords had to be retuned each time one wanted to play in a different key, right?" No they did not because only some keys would sound disagreable but not all. It is far easier to avoid certain keys than to retune an instrument; a harpsichord can be retuned but not a pipe organ. Sorry, I'm off topic. Feb27 awarded Teacher