Emanuele Paolini
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 Nov 17 answered Which is the correct way to analyse balls drawn from an urn (with replacement) Nov 17 comment A Matrix $A$ that $A^2$ is not I, but $A^4 = I$ What about rotations? Nov 15 revised Is the minimum of two metrics is again a metric? tex Nov 11 comment Is $\gamma$ homotopic to $g\circ\gamma$? I suppose that a simply connected space is also connected. In that case you can join the two starting and ending points with a continuous curve. Hence you assign the value of the homotopy $F$ on the boundary of $I\times I$. The function can then be extended on the interior by the definition of simply connectedness. If, instead, a simply connected space is not required to be connected, the statement is obviously false. Nov 11 answered Is $\gamma$ homotopic to $g\circ\gamma$? Nov 10 asked Is there a formula which gives the solutions of a general fifth grade equation by using trascendental functions? Nov 8 comment Change of variables problem. You want to plot the image of what? Please try to write a clear question. Nov 8 comment Change of variables problem. The image seems to be not related to the question. Is it? Nov 8 answered Help with summation: $\sum_{k=1}^\infty\frac{k(k+2)}{15^k}$ Nov 8 comment Non-uniqueness of solutions of an ordinary differential equation This is a gap in many courses. I have seen books which write that the solution to $x'=2\sqrt x, x(0)=0$ is $x=t^2$. Which is not only inaccurate but completely wrong for $t<0$. Nov 8 revised Non-uniqueness of solutions of an ordinary differential equation deleted 1 character in body Nov 8 answered What is the limit of $\frac{a + (n-1)d}{2a + 2(n-1)d}$ for $n \to \infty$? Nov 8 answered Non-uniqueness of solutions of an ordinary differential equation Nov 7 comment Prove that $F_n < 2^n$ for every $n \geq 0$ - Mathematical induction Proving $P(n)\Rightarrow P(n+1)$ for all $n\ge 1$ is the same as proving $P(n-1)\Rightarrow P(n)$ for all $n\ge 2$. Nov 7 answered Notation for a set $\{a_1,a_2,a_3,a_4\}$, $a_i \in \{0,1\}$ for $i = 1,2,3,4$? Nov 7 comment Prove that $F_n < 2^n$ for every $n \geq 0$ - Mathematical induction what you have written is correct. You have proved that $F_n < 2^n$ for $n\ge 2$. Why do you feel that the usual definition is something different? Nov 6 revised Applications of the formula expressing roots of a general cubic polynomial deleted 3 characters in body Nov 6 asked Applications of the formula expressing roots of a general cubic polynomial Nov 3 comment Prove the function $f(x) = (a*x)^{-1}$ is bijective Taking the inverse of both sides you get: $a*x = a*y$... This is elementary algebra, like when you want to simplify the equation $1/(7x) = 1/(7y)$. Nov 2 revised Representation of an Abelian Lie algebra english