# What is your favorite equation?

1. Dec 1, 2009

### zeromodz

It can be about anything. I am kind of new to physics and I love playing with new interesting equations like time dilation and so forth. Whats your favorite equation that you use to calculate things for fun?

2. Dec 1, 2009

### Phrak

electromagnetism: d(*+i)dA = -*J

3. Dec 1, 2009

### msbell1

Lagrange's equations

$$\frac{d}{dt}\frac{\partial L}{\partial\dot{q}} -\frac{\partial L}{\partial q}=0$$

4. Dec 2, 2009

### dE_logics

The set of equations as in the attached PDF.

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5. Dec 2, 2009

### Hootenanny

Staff Emeritus
Am I allowed two interrelated equations? If so, I'll have Maxwell's equations

$$F_{\left[\alpha\beta,\gamma\right]} = 0$$

$${F^{\alpha\beta}}_{;\beta} = \mu_0J^\alpha$$

6. Dec 2, 2009

Maxwell eqs.

7. Dec 2, 2009

### intervoxel

The symmetrization requirement in QM:

$$\psi(\textbf{r}_1,\textbf{r}_2) = \pm \psi(\textbf{r}_2,\textbf{r}_1)$$ (+for bosons, - for fermions)