# Math Help - Combinations in TeX

1. ## Combinations in TeX

We seem to spend a lot of effort typing things like ${52 \choose 5}$ in TeX.

If you examine the TeX I used for this "{52 \choose 5}", I think some of us
will save ourselves a lot of effort

RonL

2. Originally Posted by CaptainBlack
We seem to spend a lot of effort typing things like ${52 \choose 5}$ in TeX.

If you examine the TeX I used for this "{52 \choose 5}", I think some of us
will save ourselves a lot of effort

RonL
That is a good tip for the combinations problem.
Maybe, if you looked at my code you saw me using
Code:
\left(\begin{array}{c}n\\m\end{array}\right)
I asked my calculus teacher If I can give in a test answered in LaTeX. That would be fun.

3. Originally Posted by ThePerfectHacker
That is a good tip for the combinations problem.
Maybe, if you looked at my code you saw me using
Code:
\left(\begin{array}{c}n\\m\end{array}\right)
I asked my calculus teacher If I can give in a test answered in LaTeX. That would be fun.
I have been using the TeX quick reference card, where this comes from.
It can be cound on refcards.com

RonL

4. Originally Posted by CaptainBlack
I have been using the TeX quick reference card, where this comes from.
It can be cound on refcards.com

RonL
Hello,

Greetings

EB

5. I suggest that there be a sticky of common tex tags, such as the limit definition of a derivative made here to save time for all. I get sick of typing in that limit all the time.

6. Originally Posted by Jameson
I suggest that there be a sticky of common tex tags, such as the limit definition of a derivative made here to save time for all. I get sick of typing in that limit all the time.
I like the idea, I suggest CaptainBlack be its author, he seems to be the best expert in $\mathbb{T} \mathcal{E} \mathbb{X}$

7. Originally Posted by ThePerfectHacker
I like the idea, I suggest CaptainBlack be its author, he seems to be the best expert in $\mathbb{T} \mathcal{E} \mathbb{X}$
If you let me know what you want in the list I will oblige, the
difficult I will do at once; the impossible will take a little longer

RonL

8. Originally Posted by CaptainBlack
I have been using the TeX quick reference card, where this comes from.
It can be cound on refcards.com

RonL
Hello,

I've got a minor problem and as you are the best expert in TEX (as ThePerfectHacker stated) I'm sure you can help me:

I would like to write vectors with an arrow over several letters. I've attached an image to demonstrate how to do. This was made with OpenOffice where you have the command widevec{}, which doesn't work with TEX.

And the \buildrel macro doesn't work too:

$\buildrel\longrightarrow\over{A_a B_b}$

Greetings

EB

9. Originally Posted by earboth
Hello,

I've got a minor problem and as you are the best expert in TEX (as ThePerfectHacker stated) I'm sure you can help me:

I would like to write vectors with an arrow over several letters. I've attached an image to demonstrate how to do. This was made with OpenOffice where you have the command widevec{}, which doesn't work with TEX.

And the \buildrel macro doesn't work too:

$\buildrel\longrightarrow\over{A_a B_b}$

Greetings

EB
Your buildrel looks OK to me:

$
\buildrel{\longrightarrow}\over{A_b B_c}
$

Do you want an even longer arrow?

$
\overrightarrow{A_a B_b C_c D_d}
$

Interestingly this last command is not on the quick reference sheet

RonL

10. Originally Posted by CaptainBlack
...

Do you want an even longer arrow?...
RonL
Hello

$
\overrightarrow{T_h a^n k_s}
$

Greetings

EB

11. Originally Posted by earboth
Hello

$
\overrightarrow{T_h a^n k_s}
$

Greetings

EB
$
\underrightarrow{\overleftarrow{Y_ou'_r\ W^e{}_{ll}c_o{}^{me}}}
$

RonL

12. Originally Posted by Jameson
I suggest that there be a sticky of common tex tags, such as the limit definition of a derivative made here to save time for all. I get sick of typing in that limit all the time.
CaptainBlack asked for a list of tags to include. So as not to completely reinvent the wheel here, I suggest looking at this set of stickies from another math help site for ideas on that. It's a good start, but of course it doesn't have all your favorite tags.

13. Here is something I discovered.

If you want to define a piecewise function say the absolute value function what you do is:
Code:
|x|=
\left\{
\begin{array}{c}
x \mbox{ if } x\geq 0\\
-x \mbox{ if } x<0
\end{array}
\right
If that is your whole code, then you can igonore the last part.
Code:
|x|=
\left\{
\begin{array}{c}
x \mbox{ if } x\geq 0\\
-x \mbox{ if } x<0
The reason is because there is nothing following this. You cannot do this if there would be something following the code, but other here this trick works and saves me time.
----
$\left\{ \begin{array}{c} x\mbox{ if } x\geq 0\\ -x\mbox{ if } x<0$

14. how can i put a horizontal line through text i want to strike out? the \not doesn't look very good ie:
$\int \frac{dv}{\not{dt}} \not{dt}$

$\int \frac{dv}{\not{dt}} \not{dt}$