Test equation editor

Mental Calculation, Mathematics, and Puzzles
1

Cut and paste from math magic lite on my Android phone. Looking for an easy way to post math equations on the forum that are easy to read.

\begin{array}{l} {{a}^{2}\mathrm{{+}}{2}{ab}\mathrm{{+}}{b}^{2}}\\ {{a}^{3}\mathrm{{+}}{3}{a}^{2}{b}\mathrm{{+}}{3}{ab}^{2}\mathrm{{+}}{b}^{3}}\\ {{a}^{4}\mathrm{{+}}{4}{a}^{3}{b}\mathrm{{+}}{6}{a}^{2}{b}^{2}\mathrm{{+}}{4}{ab}^{3}\mathrm{{+}}{b}^{3}} \end{array}
\begin{array}{l} {{\left({{x}\mathrm{{+}}{y}}\right)}^{n}\mathrm{{=}}\mathop{\sum}\limits_{{k}\mathrm{{=}}{0}}\limits^{n}{\left({\begin{array}{c}{n}\\{k}\end{array}}\right)}{x}^{k}{y}^{{n}\mathrm{{-}}{k}}}\\ {} \end{array}

2

Test:
gif.latex?a^2&space;+2ab+b^2

Generated using online LaTeX equation editor:

3

MathJax is installed, so you can use LaTeX syntax here. Just surround the equations by dollar signs. You can use double-dollar signs for blocks, but put the dollar signs on their own lines like this:

$$
your LaTeX here
$$

Edit: I’ve removed the older instructions that were here because they don’t work on the new site.

Cheatsheet:

5 • Tip for calculating square root of complex no in mind
4

Josh , thanks a lot for embedding the MathJax notation. Very helpful !

Let’s benchmark/type the most famous math equation:

(e^{i*π} -1=0)

(I just typed: \ (e^{i*π}=1), but without the bracket between '' and ‘(’,
it works fine, btw that equation correlates all numbers: e, i,π, 0, 1, all of which are basic math concepts)

5

A favourite from high school maths,

{{ - b \pm \sqrt {{b^2} - 4ac} } \over {2a}}

*I didn’t use backslash-escaped parentheses. When I surrounded plain TeX with them, the good ol’ quadratic formula rendered but the blackslash-escaped parentheses outputted as normal text suggesting plain TeX is fine.

6

It appears that double dollar signs also work as opening and closing marks.

7

I decided to write the following Eulerian “proof” that i^i is a real number,

\begin{array}{l} {e^{ix}} = \cos x + i\sin x\\ {e^{i\frac{\pi }{2}}} = \cos \frac{\pi }{2} + i\sin \frac{\pi }{2} = o + 1i = i\\ {i^i} = {({e^{i\frac{\pi }{2}}})^i} = {e^{{i^2}\frac{\pi }{2}}} = {e^{ - \frac{\pi }{2}}} \end{array}

However when I wrote it in plain TeX, it wouldn’t render. Using LaTeX (post 2.09) and it worked immediately. I think it’s the formatting that isn’t handled with plain TeX so rather than mess around trying to fix that, we can all just use LaTeX.

P.S. When I tried to write i^i in LaTeX in the middle of a sentence, it separates it onto a new line. Any ideas on how to make it in line with the text?

8

Now if you can write the formula that defines the radius of the circle so that the primes line up in a straight line you can be added to the list with Reimann and Ramanujan.

I suspect that you will need logarithms and a flux capacitor. :slight_smile:

9

Could you paste an example of the code that isn’t working? Leave out the wrapping elements ($$ or [) so that it doesn’t render, and I’ll see if I can figure out how to get it to work.

Edit: I think I see what you are asking. You want an inline equation like: (i^i) rather than on a new line like:
[i^i]

For inline equations, use parentheses. For equations on their own lines, use square brackets (or double dollar signs).

I’ve embedded an explanation that won’t render:

10

That’s lovely, thanks Josh.