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17 Equations
In his book, In Pursuit of the Unknown: 17 Equations That Changed the World, Ian Stewart discusses each equation engagingly and practically…
Pythagorean Theorem
$$a^2 + b^2 = c^2$$
Logarithms
$$log{xy} = log{x} + log{y}$$
Calculus
$$\frac{\partial f}{\partial t} = \lim_{x\to\infty} = \frac{f{(t+h)}- f{(t)}}{h}$$
Newton’s Law of Gravity
$${F}_\text{gravity}=G\frac{m_{1}m_{2}}{r^{2}}$$
Complex Numbers
$$i^2=-1$$
Euler’s Formula for Polyhedra
$$V-E+F=2$$
Normal Distribution
$$\Phi(x)= \frac{1}{\sqrt{2\pi\rho}} e^{\frac{(x-\mu)^2}{2\rho^2}}$$
Wave Equation
$$\frac{\partial^2 u}{\partial t^2} = c^2 \frac{\partial^2 u}{\partial x^2}$$
Fourier Transform
$$f(\omega) = \int_{\infty}^{\infty}f(x)e^{-2\pi i x \omega} \text{d}x$$
Navier-Stokes Equation
$$\rho\left(\frac{d\text{v}}{dt} + \text{v} \cdot \text{v}\nabla \right) = -\nabla p + \nabla \cdot \text{T} + \text{f}$$
Maxwell’s Equations
$$\begin{aligned} &\nabla\cdot\mathcal{E} = 0 &\nabla\cdot\mathcal{H} = 0 \end{aligned}$$
$$\begin{aligned} &\nabla\times\mathcal{E} = - \frac{1}{c}\frac{\partial\mathcal{H}}{\partial t} &\nabla\times\mathcal{H} = - \frac{1}{c}\frac{\partial\mathcal{E}}{\partial t} \end{aligned}$$
Second Law of Thermodynamics
$$dS\geq0$$
Relativity
$$E=mc^2$$
Schrödinger’s Equation
$$ih \frac{\delta}{\delta t}\Psi = H\Psi$$
Information Theory
$$H=-\sum p(x) + log{p(x)}$$
Chaos Theory
$$x_{t+1} = kx_t(1-x_i)$$
Black-Scholes Equation
$$\frac{1}{2}\sigma^2S^2 \frac{\delta^2 V}{\delta S^2} + rS \frac{\delta V}{\delta S} + \frac{\delta V}{\delta t} - rV = 0$$