## 🧮 Favorite and important mathematical formulas

**Euler's identity a'la the world's most beautiful mathematical formula:**

$${\displaystyle e^{i\pi }+1=0}$$

**Equivalence of mass and energy described by Albert Einstein:**

$$E=mc^{2}$$

$${\displaystyle {\hat {f}}(\xi )=\int _{-\infty }^{\infty }f(x)\ e^{-i2\pi \xi x}\,dx,\quad \forall \ \xi \in \mathbb {R} .}$$

The positional-spatial Schrödinger equation for a single non-relativistic particle in one dimension:

$${\displaystyle i\hbar {\frac {\partial }{\partial t}}\Psi (x,t)=\left[-{\frac {\hbar ^{2}}{2m}}{\frac {\partial ^{2}}{\partial x^{2}}}+V(x,t)\right]\Psi (x,t)}$$

Residue (complex analysis):

$${\displaystyle \mathrm {Res} (f,z_{0})={\frac {1}{2\pi i}}\oint \limits _{\gamma }f(z)\ \operatorname {d} z,}$$

Gauss's law

$$\oiint _{\partial \Omega }\mathbf {E} \cdot \mathrm {d} \mathbf {S} ={\frac {1}{\varepsilon _{0}}}\iiint _{\Omega }\rho \,\mathrm {d} V$$

Gauss's law for magnetism

$$\oiint _{\partial \Omega }\mathbf {B} \cdot \mathrm {d} \mathbf {S} =0$$

$$\oint _{\partial \Sigma }\mathbf {E} \cdot \mathrm {d} {\boldsymbol {\ell }}=-{\frac {\mathrm {d} }{\mathrm {d} t}}\iint _{\Sigma }\mathbf {B} \cdot \mathrm {d} \mathbf {S}$$