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The following is basic information about our forum. Please read this before posting questions or answers if you are unfamiliar with this sort of forum. Click on any question to show or hide the answer.

What kinds of questions can I ask here?

Most importantly, questions should be **relevant to our community**. Before you ask, please make sure to search for a similar question. You can search for questions by their title or tags.

What kinds of questions should be avoided?

Please avoid asking questions that are not related to our community, too subjective or argumentative.

What should I avoid in my answers?

Dettonville Answers is a **question and answer** site - it is **not** a discussion group. Please avoid holding debates in your answers as they tend to dilute the quality of the forum.

For brief discussion, or to thank someone for their answer, please post comments, not answers.

For brief discussion, or to thank someone for their answer, please post comments, not answers.

How to enter mathematical notation?

For **Greek letters**, use `\alpha`

, `\beta`

, …, `\omega`

: $\alpha, \beta, … \omega$. For uppercase, use `\Gamma`

, `\Delta`

, …, `\Omega`

: $\Gamma, \Delta, …, \Omega$.

For **superscripts and subscripts**, use `^`

and `_`

. For example, `x_i^2`

: $x_i^2$.

By default, superscripts, subscripts, and other operations apply only to the next "group". A "group" is either a single symbol, or any formula surrounded by curly braces `{`

…`}`

. If you do `10^10`

, you will get a surprise: $10^10$. But `10^{10}`

gives what you probably wanted: $10^{10}$. Use curly braces to delimit a formula to which a superscript or subscript applies: `x^5^6`

is an error; `{x^y}^z`

is ${x^y}^z$, and `x^{y^z}`

is $x^{y^z}$. Observe the difference between `x_i^2`

$x_i^2$ and `x_{i^2}`

$x_{i^2}$.

**Parentheses** Ordinary symbols `()[]`

make parentheses and brackets $(2+3)[4+4]$. Use `\{`

and `\}`

for curly braces $\{\}$.

These do *not* scale with the formula in between, so if you write `(\frac12)`

the parentheses will be too small: $(\frac12)$. Using `\left(`

…`\right)`

will make the sizes adjust automatically to the formula they enclose: `\left(\frac12\right)`

is $\left(\frac12\right)$.

`\left`

and`\right`

apply to all the following sorts of parentheses: `(`

and `)`

$(x)$, `[`

and `]`

$[x]$, `\{`

and `\}`

$\lbrace x \rbrace$, `|`

$|x|$, `\langle`

and `\rangle`

$\langle x \rangle$, `\lceil`

and `\rceil`

$\lceil x \rceil$, and `\lfloor`

and `\rfloor`

$\lfloor x \rfloor$. There are also invisible parentheses, denoted by `.`

: `\left.\frac12\right\rbrace`

is $\left.\frac12\right\rbrace$.

**Sums and integrals** `\sum`

and `\int`

; the subscript is the lower limit and the superscript is the upper limit, so for example `\sum_1^n`

$\sum_1^n$. Don't forget `{`

…`}`

if the limits are more than a single symbol. For example, `\sum_{i=0}^\infty i^2`

is $\sum_{i=0}^\infty i^2$. Similarly, `\prod`

$\prod$, `\int`

$\int$, `\bigcup`

$\bigcup$, `\bigcap`

$\bigcap$, `\iint`

$\iint$.

**Fractions** There are two ways to make these. `\frac ab`

applies to the next two groups, and produces $\frac ab$; for more complicated numerators and denominators use `{`

…`}`

: `\frac{a+1}{b+1}`

is $\frac{a+1}{b+1}$. If the numerator and denominator are complicated, you may prefer `\over`

, which splits up the group that it is in: `{a+1\over b+1}`

is ${a+1\over b+1}$.

For inline formulas, enclose the formula in `\(...\)`

. For displayed formulas, use `$$...$$`

.

These render differently as can be seen in the following two examples:

`"\(\sum_{i=0}^n i^2 = \frac{(n^2+n)(2n+1)}{6}\)"`

appears as \(\sum_{i=0}^n i^2 = \frac{(n^2+n)(2n+1)}{6}\) (inline)

whereas

`"$$\sum_{i=0}^n i^2 = \frac{(n^2+n)(2n+1)}{6}\tag{displayed}$$"`

appears as $$\sum_{i=0}^n i^2 = \frac{(n^2+n)(2n+1)}{6}\tag{displayed}$$

**Fonts**

- Use
`\mathbb`

or`\Bbb`

for "blackboard bold": $\mathbb{CHNQRZ}$. - Use
`\mathbf`

for boldface: $\mathbf{ABCDEFGHIJKLMNOPQRSTUVWXYZ}$ $\mathbf{abcdefghijklmnopqrstuvwxyz}$. - Use
`\mathtt`

for "typewriter" font: $\mathtt{ABCDEFGHIJKLMNOPQRSTUVWXYZ}$ $\mathtt{abcdefghijklmnopqrstuvwxyz}$. - Use
`\mathrm`

for roman font: $\mathrm{ABCDEFGHIJKLMNOPQRSTUVWXYZ}$ $\mathrm{abcdefghijklmnopqrstuvwxyz}$. - Use
`\mathcal`

for "calligraphic" letters: $\mathcal{ ABCDEFGHIJKLMNOPQRSTUVWXYZ}$ - Use
`\mathscr`

for script letters: $\mathscr{ABCDEFGHIJKLMNOPQRSTUVWXYZ}$ - Use
`\mathfrak`

for "Fraktur" (old German style) letters: $\mathfrak{ABCDEFGHIJKLMNOPQRSTUVWXYZ} \mathfrak{abcdefghijklmnopqrstuvwxyz}$.

**Radical signs** Use `sqrt`

, which adjusts to the size of its argument: `\sqrt{x^3}`

$\sqrt{x^3}$; `\sqrt[3]{\frac xy}`

$\sqrt[3]{\frac xy}$. For complicated expressions, consider using `{...}^{1/2}`

instead.

Some special functions such as "lim", "sin", "max", "ln", and so on are normally set in roman font instead of italic font. Use `\lim`

, `\sin`

, etc. to make these: `\sin x`

$\sin x$, not `sin x`

$sin x$. Use subscripts to attach a notation to `\lim`

: `\lim_{x\to 0}`

$$\lim_{x\to 0}$$

There are a very large number of special symbols and notations, too many to list here; see this shorter listing, or this exhaustive listing. Some of the most common include:

`\lt \gt \le \ge \neq`

$\lt\, \gt\, \le\, \ge\, \neq$. You can use`\not`

to put a slash through almost anything:`\not\lt`

$\not\lt$ but it often looks bad.`\times \div \pm \mp`

$\times\, \div\, \pm\, \mp$.`\cdot`

is a centered dot: $x\cdot y$`\cup \cap \setminus \subset \subseteq \subsetneq \supset \in \notin \emptyset \varnothing`

$\cup\, \cap\, \setminus\, \subset\, \subseteq \,\subsetneq \,\supset\, \in\, \notin\, \emptyset\, \varnothing$`{n+1 \choose 2k}`

or`\binom{n+1}{2k}`

${n+1 \choose 2k}$`\to \rightarrow \leftarrow \Rightarrow \Leftarrow \mapsto`

$\to\, \rightarrow\, \leftarrow\, \Rightarrow\, \Leftarrow\, \mapsto$`\land \lor \lnot \forall \exists \top \bot \vdash \vDash`

$\land\, \lor\, \lnot\, \forall\, \exists\, \top\, \bot\, \vdash\, \vDash$`\star \ast \oplus \circ \bullet`

$\star\, \ast\, \oplus\, \circ\, \bullet$`\approx \sim \cong \equiv \prec`

$\approx\, \sim \, \cong\, \equiv\, \prec$.`\infty \aleph_0`

$\infty\, \aleph_0$`\nabla \partial`

$\nabla\, \partial$`\Im \Re`

$\Im\, \Re$- For modular equivalence, use
`\pmod`

like this:`a\equiv b\pmod n`

$a\equiv b\pmod n$. `\ldots`

is the dots in $a_1, a_2, \ldots ,a_n$`\cdots`

is the dots in $a_1+a_2+\cdots+a_n$- Some Greek letters have variant forms:
`\epsilon \varepsilon`

$\epsilon\, \varepsilon$,`\phi \varphi`

$\phi\, \varphi$, and others. Script lowercase l is`\ell`

$\ell$.

Who moderates this community?

The short answer is: **you.** This website is moderated by the users. Points system allows users to earn rights to perform a variety of moderation tasks.

How does point system work?

When a question or answer is voted up, the user who posted it will gain points. These points serve as a rough measure of the community trust in that person. Various moderation tasks are gradually assigned to the users based on those points.

For example, if you ask an interesting question or useful answer, it will likely be voted up. On the other hand if the question is poorly-worded or the answer is misleading - it will likely be voted down. Each up vote on a question will generate**1 points**, whereas each vote against will subtract **1 points**. The following table lists points gained per activity:

The following table lists point requirements for each type of moderation task.

The following table lists the user titles based on points:

For example, if you ask an interesting question or useful answer, it will likely be voted up. On the other hand if the question is poorly-worded or the answer is misleading - it will likely be voted down. Each up vote on a question will generate

Posting a question: | 20 points |

Selecting an answer for your question: | 30 points |

Per up vote on your question: | + 10 points |

Per down vote on your question: | - 10 points |

Limit from up votes on each question: | + 100 points |

Limit from down votes on each question: | – 30 points |

Posting an answer: | 40 points |

Having your answer selected as the best: | 300 points |

Per up vote on your answer: | + 20 points |

Per down vote on your answer: | - 20 points |

Limit from up votes on each answer: | + 200 points |

Limit from down votes on each answer: | – 50 points |

Voting up a question: | 10 points |

Voting down a question: | 10 points |

Voting up an answer: | 10 points |

Voting down an answer: | 10 points |

Add for all users: | + 100 points |

The following table lists point requirements for each type of moderation task.

Voting posts down | 100 points |

Voting on answers | 100 points |

Voting on questions | 100 points |

The following table lists the user titles based on points:

Wizard - 250,000 points

Necromancer - 128,000 points

Sorcerer - 64,000 points

Warlock - 32,000 points

Enchanter - 16,000 points

Magician - 8,000 points

Thaumaturgist - 4,000 points

Theurgist - 2,000 points

Conjurer - 1,000 points

Evoker - 500 points

Prestidigitator - 50 points

How to change my picture (gravatar), and what is gravatar?

The picture that appears in user profiles is called a **gravatar**, which means **globally recognized avatar**.

Here is how it works: You upload your picture (or your favorite alter ego image) to the website**gravatar.com** from where we later retrieve your image using a cryptographic key based on your email address.

This way all the websites you trust can show your image next to your posts and your email address remains private.

Please**personalize your account with an image** - just register at **gravatar.com** (just please be sure to use the same email address that you used to register with us). The default gray image is generated automatically.

Here is how it works: You upload your picture (or your favorite alter ego image) to the website

This way all the websites you trust can show your image next to your posts and your email address remains private.

Please

What is proper forum etiquette?

The rules on etiquette on this site are very simple – be nice, be honest and speak to others as you expect others to speak to you.

Be warned – repeat offenders will be kicked off this site. Sure you can rejoin under a new email but you’ll lose all your hard earned rep and will end up booted off again if you break the rules.

Don’t flame on others if it seems they don’t know as much as you – be tolerant. Everyone on this site is here to learn and teach.

If you see poor or misguiding information, vote it down. Add comments indicating what, specifically, is wrong. Provide better answers of your own. It's your input that helps keep this site free from poor quality content as well as builiding up your own reputation.

Be warned – repeat offenders will be kicked off this site. Sure you can rejoin under a new email but you’ll lose all your hard earned rep and will end up booted off again if you break the rules.

Don’t flame on others if it seems they don’t know as much as you – be tolerant. Everyone on this site is here to learn and teach.

If you see poor or misguiding information, vote it down. Add comments indicating what, specifically, is wrong. Provide better answers of your own. It's your input that helps keep this site free from poor quality content as well as builiding up your own reputation.

Do I have to register to use the site?

You don’t have to register to view questions and answers, but you’ll get much more out of this site if you do.

You have to register to ask and answer questions as well as add comments. Only registered users can vote and receive points & badges.

Registration is quick & simply and requires only your name, email and a password.

You have to register to ask and answer questions as well as add comments. Only registered users can vote and receive points & badges.

Registration is quick & simply and requires only your name, email and a password.

Still have questions?

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