General ⇒ 2 more math questions

[Snoop1990]

Hey,
I have two more math question.

1. I want to write an arrow with a function name above:
I first tried

Code: Select all

\rightarrow^f

but this places the f at the end not in the middle. So I tried

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\stackrel{f}{\rightarrow}

now it is up and in the middle but it should be a bit smaller. I guess I am just missing some function, so please help.

2. I want to define a function that is not constantly:

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|x| := \begin{Bmatrix}x & for &x \leq 0 \\-x & for& x<0\end{matrix}

This worked with my last LaTeX Render, but now he complains about the \end tag. But I do not want the bracket at the end. So again I guess there is a command I do not know ...

I am sorry but I am no native speaker therefore my english especially when it comes to mathematical expressions is bad, hope you understand what I am looking for if not, feel free to ask.

Regrades Snoop1990

[shmill]

[quote="Snoop1990"]Hey,
I have two more math question.

1. I want to write an arrow with a function name above:
I first tried

Code: Select all

\rightarrow^f

but this places the f at the end not in the middle. So I tried

Code: Select all

\stackrel{f}{\rightarrow}

now it is up and in the middle but it should be a bit smaller. I guess I am just missing some function, so please help.


try \buildrel{f}\over{\rightarrow}

[localghost]

The first solution works with standard LaTeX. For the second one you have to include the (preferably to use) amsmath package.

1. You can control the font size in math mode. Just add a suitable command.

   Code: Select all

   \[
     \stackrel{\scriptstyle f}{\longrightarrow}
   \]
   

   Refer to basic LaTeX documentation to learn more about sizes in displayed mode.
2. Use the cases environment to get what you want.

   Code: Select all

   \[
     |x| := \begin{cases}\hphantom{-}x & \text{for}\quad x\geq 0 \\-x & \text{for}\quad x<0\end{cases}
   \]

   I added a virtual "-" to get a proper alignment.

More about typesetting mathematical expressions can be found in "Math mode".


Best regards
Thorsten¹

[Snoop1990]

...

Thank you very much that is exactly what I was looking for !

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