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Daily Insights from Magic Internet Math courses. Learn at https://mathacademy-cyan.vercel.app
πŸ“ Economic Calculation Problem Without market prices, central planners cannot calculate whether resources are being used efficiently. This is the fundamental problem that makes rational socialist planning impossible. Proof: To allocate resources rationally, one must know the relative values of different uses. Prices emerge only from voluntary exchange. Socialism abolishes private ownership of means of production. Without private ownership, there is no exchange of capital goods. Without exchange, there are no... From: Human Action Learn more: Explore all courses:
πŸ“– Prometheus Unchained John Galt is Prometheus who changed his mindβ€”after centuries of being torn by vultures for bringing fire to men, he withdrew his fire until men withdraw their vultures. From: Atlas Shrugged Learn more: Explore all courses:
πŸ“ Euclid Given any finite list of primes $p_1, p_2, \\ldots, p_k$, there exists a prime not on this list. Proof: Consider $n = p_1 p_2 \\cdots p_k + 1$. By the Lemma, $n$ has some prime divisor $p$. But $n \\equiv 1 \\pmod{p_i}$ for each $i$, so $p$ cannot equal any $p_i$. Therefore there exists a prime not on the original list. Since any finite list can be extended, there are infinitely many primes. From: Thales to Euclid Learn more: Explore all courses:
πŸ“– Vertex and Edge Connectivity The vertex connectivity $\\kappa(G)$ is the minimum size of a vertex cut (or $n-1$ if $G = K_n$). The edge connectivity $\\kappa\ From: Introduction to Graph Theory Learn more: Explore all courses:
πŸ“ Rank-Nullity Theorem (Dimension Theorem) If $V$ is finite-dimensional, then $T(V)$ is also finite-dimensional, and: $\\dim N(T) + \\dim T(V) = \\dim V$. In other words, the nullity plus the rank of a linear transformation equals the dimension of its domain. Proof: Let $n = \\dim V$ and let $e_1, \\ldots, e_k$ be a basis for $N(T)$ where $k = \\dim N(T)$. By Theorem 1.7, these are part of some basis for $V$: $e_1, \\ldots, e_k, e_{k+1}, \\ldots, e_n$ where $k + r = n$. We show that $T(e_{k+1}), \\ldots, T(e_n)$ form a basis for $T(V)$, proving $\\dim T(V) =... From: calc2 Learn more: Explore all courses:
πŸ“ Fundamental Theorem of Calculus (Part 1) If $f$ is continuous on $[a, b]$ and $F(x) = \\int_a^x f(t)\\,dt$, then $F$ is differentiable and $F\ Proof: The derivative of an accumulation function is the original function. If you're accumulating something at rate $f(x)$, then the rate of change of your total is exactly $f(x)$. Formally: $F'(x) = \\lim_{h \\to 0} \\frac{F(x+h) - F(x)}{h} = \\lim_{h \\to 0} \\frac{1}{h}\\int_x^{x+h} f(t)\\,dt = ... From: Calculus: A Liberal Art Learn more: Explore all courses:
πŸ“ Cayley-Hamilton Theorem Every linear operator satisfies its characteristic polynomial: if $p(t) = \\det(tI - A)$, then $p(A) = 0$. Proof: The minimal polynomial divides the characteristic polynomial by structure theory. Since both are monic of the same degree when considering the module $F[t]/(m_\\tau)$, they are equal up to units. From: adv_linalg Learn more: Explore all courses:
πŸ“– Leibniz Notation for Derivatives The derivative is written as $\\frac{dy}{dx}$, representing the ratio of infinitesimal changes. This notation suggests correctly that derivatives behave like fractions. From: Calculus: A Liberal Art Learn more: Explore all courses:
πŸ“ Sample Theorem If $A \\subseteq B$ and $B \\subseteq A$, then $A = B$ Proof: Let $x \\in A$. Since $A \\subseteq B$, we have $x \\in B$ by definition of subset. Therefore, every element of $A$ is in $B$. Now, let $y \\in B$. Since $B \\subseteq A$, we have $y \\in A$ by definition. Therefore, every element of $B$ is in $A$. Since $A \\subseteq B$ and $B \\subseteq A... From: foundation Learn more: Explore all courses:
πŸ“ Fundamental Theorem of Arithmetic Every positive integer greater than $1$ has a unique factorization into prime numbers (up to order). From: Thales to Euclid Learn more: Explore all courses:
πŸ“– Field A field $F$ is a set with addition and multiplication where $(F, +)$ is an abelian group, $(F \\setminus \\{0\\}, \\cdot)$ is an abelian group, and distributivity holds. From: Algebraic Number Theory Learn more: Explore all courses:
πŸ“ Hyperbolic Isometries The isometries of the Poincare disk are the Mobius transformations that preserve the unit disk. These have the form $z \\mapsto e^{i\\theta}\\frac{z - a}{1 - \\bar{a}z}$ for $|a| < 1$. From: Four Pillars of Geometry Learn more: Explore all courses:
πŸ“ Theorem 7.12 (Uniform Limit of Continuous) If $f_n \\to f$ uniformly on $E$ and each $f_n$ is continuous on $E$, then $f$ is continuous on $E$. Proof: Fix $x \\in E$ and $\\varepsilon > 0$. By uniform convergence, there exists $N$ with $|f_n(t) - f(t)| < \\varepsilon/3$ for all $t \\in E$ when $n \\geq N$. Since $f_N$ is continuous at $x$, there exists $\\delta > 0$ with $|f_N(t) - f_N(x)| < \\varepsilon/3$ when $|t - x| < \\delta$. Then for... From: rudin Learn more: Explore all courses:
πŸ’‘ Tocqueville\ "Democracy extends the sphere of individual freedom, socialism restricts it. Democracy attaches all possible value to each man; socialism makes each man a mere agent. Democracy and socialism have nothing in common but one word: equality. But notice the difference: while democracy seeks equality in liberty, socialism seeks equality in restraint and servitude." From: The Road to Serfdom Learn more: Explore all courses:
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