In his book, In Pursuit of the Unknown: 17 Equations That Changed the World, Ian Stewart discusses each equation engagingly and practically…

$$a^2 + b^2 = c^2$$

$$log{xy} = log{x} + log{y}$$

$$\frac{\partial f}{\partial t} = \lim_{x\to\infty} = \frac{f{(t+h)}- f{(t)}}{h}$$

$${F}_\text{gravity}=G\frac{m_{1}m_{2}}{r^{2}}$$

$$i^2=-1$$

$$\begin{aligned} &\nabla\cdot\mathcal{E} = 0 &\nabla\cdot\mathcal{H} = 0 \end{aligned}$$

$$\begin{aligned} &\nabla\times\mathcal{E} = - \frac{1}{c}\frac{\partial\mathcal{H}}{\partial t} &\nabla\times\mathcal{H} = - \frac{1}{c}\frac{\partial\mathcal{E}}{\partial t} \end{aligned}$$

$$dS\geq0$$

$$E=mc^2$$

$$H=-\sum p(x) + log{p(x)}$$

$$x_{t+1} = kx_t(1-x_i)$$