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 Apr 13 comment Given three coordinates (a,b,c), (d,e,f), and (l,m,n), what is the center of the circle in the 3D plane (h,k,i) that contains these three points. Drop perpendiculars from two segments joining pairs of the given points and find where they meet. Apr 13 revised Quotient Group Isomorphic to $\mathbb{Z}_{3}$? added 64 characters in body Apr 13 answered Quotient Group Isomorphic to $\mathbb{Z}_{3}$? Jan 29 comment Why is integration so much harder than differentiation? Differentiation is more difficult. Jan 11 comment Obtaining an estimate for the Lagrangian $L=H^*$ from the Hamiltonian $H$ Wonderful, thanks. Jan 11 accepted Obtaining an estimate for the Lagrangian $L=H^*$ from the Hamiltonian $H$ Jan 11 comment Obtaining an estimate for the Lagrangian $L=H^*$ from the Hamiltonian $H$ @epimorphic using $v_1$ and $v_2$ such that $L(v_j)=p_j\cdot v_j - H(p_j), j=1,2.$ Jan 8 awarded Nice Question Jan 4 comment Obtaining an estimate for the Lagrangian $L=H^*$ from the Hamiltonian $H$ @user226970 I see how that works out now, thanks. I saw a hint in some notes that points to another way of doing it so I'll hold out to see if anyone comes up with an alternative. Jan 3 comment An exemple of measurable function $f$ on $\mathbb R^2$ s.t. $f^y$ is not mesurable for every $y$. Ok. Then your example works. Be careful with your English. Change "every" to "some". Jan 3 comment An exemple of measurable function $f$ on $\mathbb R^2$ s.t. $f^y$ is not mesurable for every $y$. @user301068 You want $f^y$ to be nonmeasurable for every $y,$ right? Jan 3 comment An exemple of measurable function $f$ on $\mathbb R^2$ s.t. $f^y$ is not mesurable for every $y$. When $y=1$, $f^y\equiv 0,$ which is measurable. Jan 3 comment Global Lyapunov function. Definition You get $+\infty$ in some directions and $-\infty$ in others. Namely, when $y=0$ you get $\infty$ as $x\to -\infty,$ $-\infty$ as $x\to \infty$. So, there is no limit. Jan 3 comment Global Lyapunov function. Definition @Rhjg Yes, I've edited it. Jan 3 revised Global Lyapunov function. Definition added 10 characters in body Jan 3 answered Global Lyapunov function. Definition Jan 1 comment Obtaining an estimate for the Lagrangian $L=H^*$ from the Hamiltonian $H$ @mvw newer editions have $v_1, v_2$ instead of $q_1, q_2.$ Jan 1 asked Obtaining an estimate for the Lagrangian $L=H^*$ from the Hamiltonian $H$ Dec 8 awarded Notable Question Oct 26 awarded Nice Question