# Using TeX Notation

Note: This page is a work-in-progress. Feedback and suggested improvements are welcome. Please join the discussion on moodle.org or use the page comments.

TeX (pronounced TEK) is a very widespread and popular way of representing Mathematics notation using only characters that you can type on a keyboard (see Wikipedia). This makes it a useful format to use in Moodle, since it can be entered anywhere you can type text, from forum posts to quiz questions.

TeX expressions can be entered in multiple ways:

• typing them directly into texts.
• using the Java-based Dragmath editor in Moodle's TinyMCE editor.
• using the HTML-based equation editor in Moodle's Atto editor (since Moodle 2.7).

Afterwards, TeX expressions are rendered into Mathematics notation:

• using the TeX filter in Moodle, which uses a TeX binary installed on the server to convert expressions into .gif images (or if that is not available, it falls back to a simple built-in mimetex binary).
• using the MathJax_filter which identifies TeX expressions and uses the Mathjax JS library to render them in browsers at display time (since Moodle 2.7).
• using other third-party solutions.

As you can imagine, the whole field is not simple as we'd like, especially because there are many flavours of TeX and slight variations between tools.

WARNING: This Wiki environment uses a DIFFERENT TeX renderer to Moodle, especially when it comes to control sequences. For this reason images are sometimes used to represent what it should look like in Moodle. YMMV.

## Lines

Warning: Drawing lines in TeX Notation in Moodle is an issue, go to the Using Text Notation for more information. If the line is not noted properly then the parser will try to correctly draw the line but will not successfully complete it. This means that every image that needs be drawn will be drawn until it hits the error. When the error is being converted, it fails, so no subsequent image is drawn. Be careful and make sure your line works BEFORE you move to the next problem or next image.

 a couple of lines $$\red \picture(200){(20,0){ \line(180,0)}{(20,180){\line(180,0}$$ The structure of the picture box is that the \picture(200) provides a square image template. The (20,0) provides the starting coordinates for any line that comes after. In this case the start point is at 20pixels in the x axis and 0 pixels in the y axis. The starting point for all coordinates, 0,0, is the bottom left corner and they run in a clockwise manner. Do not confuse this with arcs. The \line(180,0) determines the length and inclination of the line. In this case, the inclination is 0 and the length is 180px. These are enclosed in braces, all inside one set of braces owned by the \picture() control sequence. The next set of commands are the same, that is, the (20,200) are the coordinates of the next line. The x co-ordinate is the 20, that is the distance to the right from the 0 point. The y co-ordinates is the distance from the bottom of the image. Whereas the first line started and ran on the bottom of the picture frame, the y co-ordinate starts at the 200 pixel mark from the bottom of the image. The line, at 180 pixels long and has no y slope. This creates a spread pair of parallel lines. \picture explained

While this explains the structure of a line, there is a couple of elements that you need to go through to do more with them.

## Squares and Rectangles

Drawing squares and rectangles is similar, but only slightly different.

There should be a square box tool, and there is, but unless it has something inside it, it does not display. It is actually easier to make a square using the \line command.

 This box is constructed using: $$\picture(250){(10,10){\line(0,230)}(10,10){\line(230,0)}(240,10){\line(0,230)}(10,240){\line(230,0)}}$$ It is a 250 pixel square box with a 230 pixel square inside it. This box is different in that is has the equal length indicators that are used in a square. $$\picture(250){(10,10){\line(0,230)} (5,120){\line(10,0)} (10,10){\line(230,0)} (120,5){\line(0,10)} (240,10){\line(0,230)} (235,120){\line(10,0)} (10,240){\line(230,0)} (120,235){\line(0,10)}}$$ The rectangle then becomes the same thing, but with one side shorter. For a portrait canvas it would be: $$\picture(250){(10,10){\line(0,230)}(10,10){\line(150,0)}(160,10){\line(0,230)}(10,240){\line(150,0)}}$$ The rectangle can also produce a landscape shape: $$\picture(250){(10,10){\line(0,160)}(10,10){\line(230,0)}(240,10){\line(0,160)}(10,170){\line(230,0)}}$$

## Controlling Angles

Controlling angles is a little different. They involve a different perception, but not one that is unfamiliar. Consider this:

We have a point from which we want to draw a line that is on an angle. The notation used at this point can be positive, positive or positive, negative or negative, positive or negative, negative. Think of it like a number plane or a graph, using directed numbers. The 0,0 point is in the centre, and we have four quadrants around it that give us one of the previously mentioned results.

 $$\picture(100){(50,50){\line(40,45)}}$$, a positive x and positive y $$\picture(100){(50,50){\line(-40,45)}}$$ a negative x and positive y $$\picture(100){(50,50){\line(-40,-45)}}$$ a negative x and negative y $$\picture(100){(50,50){\line(40,-45)}}$$ a positive x and a negative y

Essentially, what these points boil down to is that anything above the insertion point is a positive on the y axis, anything below is a negative. Anything to the left of the insertion point is a negative while everything to the right is a positive.

 $$\picture(100){(50,50){\line(40,45)}(50,50){\line(-40,45)}(50,50){\line(-40,-45)}(50,50){\line(40,-45)}}$$ The co-ordinate alignment process in TeX is not that good that you can use one set of co-ords as a single starting point for all lines. The layering of each object varies because of the position of the previous object, so each object needs to be exactly placed. This co-ord structure has a great deal of impact on intersecting lines, parallel lines and triangles.

## Intersecting Lines

You can set up an intersecting pair easily enough, using the \picture control sequence.

 $$\picture(200){(10,0){\line(150,150)} (0,130){\line(180,-180)}}$$ The lines that are drawn can be labeled. $$\picture(200){(10,0){\line(150,150)}(0,130){\line(180,-180)} (0,10){A}(0,135){B}(140,0){C}(140,150){D}(62,80){X}}$$ To produce another image. To which you may want to ask the question: $$The \ \angle \ of \ AXB \ is \ 72\textdegree. \ What \ is \ the \ value \ of \ \angle BXD?$$ NOTE: Labeling this image, above-right, turned out to be fairly simple. Offsetting points by a few pixels at the start or end points of the lines proved a successful strategy. The X point proved a little more problematic, and took a number of adjustments before getting it right. Experience here will help. With labels the drawing can become a little more like your traditional geometric drawing, but the devil is in the details. The parallel markers need to be placed properly, and that is where experience really comes into it. On lines that are vertical or horizontal, you can get away with using the > or < directly from the keyboard, or the ${\displaystyle \ll }$ or ${\displaystyle \theta }$ symbols. In either case, you need to position them properly. The code: $$\picture(200){(15,45){\line(170,0)} (15,30){c}(170,28){d}(15,160){\line(170,0)}(15,145){e}(180,143){f}(50,20){\line(110,175)}(58,20){a}(140,185){b}(42,32){\kappa}(53,48){\beta} (150,165){\kappa} (90,38){\gg}(80,153){\gg} }$$

## Lines and Arcs

Combining lines and arcs is a serious challenge actually, on a number of levels. For example lets take an arc from the first page on circles.

 File:line11.gif Fairly innocuous of itself, but when we start to add in elements, it changes dramatically. $$\circle(120;90,180)$$ $$\picture(150){(75,75){\circle(120;90,180)}(75,75){\line(-70,0)}(75,75){\line(0,75)}}$$ All elements in this drawing start in the same place. Each is layered, and properly placed on the canvas, and using the same co-ord to start makes it easy to control them. No matter the size of the arc, intersecting lines can all be drawn using the centre co-ords of the arc.

## Triangles

Of all the drawing objects, it is actually triangles that present the most challenge. For example:

 $$\picture(350){(10,10){\line(0,320)}(10,330){\line(330,0)}(10,10){\line(330,320)}}$$ This is a simple triangle, one that allows us to establish a simple set of rules for the sides. The vertical always has an x=0 co-ord and the horizontal always has a y=0 co-ord. In this case with an x value of 330 on the horizontal, and a y value of 320 on the vertical, the hypotenuse should then have a value of x=340, and the y=330, but not so, they actually have an x=330 and a y=320. There is no need to add the starting point co-ords to the x and y values of the line. $$picture(350){(10,10){\line(330,0)}(340,10){\line(0,320)}(340,330){\line(-330,-320)}}$$

This triangle has been developed for a Trigonometry page - but the additional notation should provide insight into how you can use it.

 This is a labeled image, but it has an \fbox in it with its little line. With some effort, it could be replaced with two intersecting short lines. $$\picture(350,150){(25,25){\line(300,0)}(325,25){\line(0,110)}(25,25){\line(300,110)}(309,25){\fbox{\line(5,5)}} (307,98){\theta}(135,75){\beta}(150,5){\alpha}(335,75){\epsilon}}$$

 The triangle shows like: We use the different elements of the triangle to identify those things we need to know about a right-angled triangle. The hypotenuse is always the side that is opposite the right angle. The longest side is always the Hypotenuse. To identify the other elements of the triangle we look for the sign ${\displaystyle \Theta }$. ${\displaystyle \angle \theta }$ is the starting point for naming the other sides. The side that is opposite ${\displaystyle \angle \theta }$ is known as the Opposite. The side that lies alongside ${\displaystyle \angle \theta }$ is known as the Adjacent side. To determine which is which, draw a line that bisects ${\displaystyle \angle \theta }$ and whatever line it crosses is the Opposite side. The code: $$\picture(350,250){(25,25){\line(300,0)}(25,25){\line(0,220)}(25,245){\line(300,-220)}(310,25){\circle(100;135,180)}(20,100){\line(310,-75)} (25,25){\fbox{\line(5,5)}}(25,25){\line(150,150)}(165,140){Hypotenuse}(120,2){Adjacent}(2,80){\rotatebox{90}{Opposite}}(270,40){\theta}}$$

# Matrices

A Matrix is a rectangular array of numbers arranged in rows and columns which can be used to organize numeric information. Matrices can be used to predict trends and outcomes in real situations - i.e. polling.

## A Matrix

A matrix can be written and displayed like

In this case the matrix is constructed using the brackets before creating the array:

 $$M = \left[\begin{array}{ccc} a&b&1 \ c&d&2 \ e&f&3\end{array}\right]$$


The internal structure of the array is generated by the &, ampersand, and the double backslash.

You can also create a grid for the matrix.

 A dashed line A solid line A mixed line $$M = \left[\begin{array}{c.c.c} a&b&1 \ \hdash c&d&2 \ \hdash e&f&3\end{array}\right]$$ c|c} a&b&1 \ \hline c&d&2 \ \hline e&f&3\end{array}\right] $$c} a&b&1 \ \hline c&d&2 \ \hdash e&f&3\end{array}\right]$$

The command sequences here are the {c|c.c} and \hdash and \hline. The pipe, |, and the full stop determine the line type for the vertical line.

Matrices also respond to other TeX Notation commands such as size and colour.

 Colour Size $$\blue M = \left[\begin{array}{c.c.c} a&b&1 \ \hdash c&d&2 \ \hdash e&f&3\end{array}\right]$$ $$\fs7 M = \left[\begin{array}{c.c.c} a&b&1 \ \hdash c&d&2 \ \hdash e&f&3\end{array}\right]$$ $$\fs2 M = \left[\begin{array}{c.c.c} a&b&1 \ \hdash c&d&2 \ \hdash e&f&3\end{array}\right]$$

## Creating equal and unequal matrices

Equal and unequal matrices are simply matrices that either share or not share the same number of rows and columns. To be more precise, equal matrices share the same order and each element in the corresponding positions are equal. Anything else is unequal matrices.

Actually equal and unequal matrices are constructed along similar lines, but have different shapes:

 Equal Matrix An unequal matrix $$\left[\begin{array} a&b&1 \ c&d&2 \ e&f&3\end{array}\right] \ = \ \left[\begin{array} 12&11&z \ 10&9&y \ 8&7&x\end{array}\right]$$ $$\left[\begin{array} a&b \ c&d \ e&f \end{array}\right] \ \neq \ \left[\begin{array} 12&11&z \ 10&9&y \ 8&7&x\end{array}\right]$$

## Labeling a Matrix

Addition and subtraction matrices are similar again, but the presentation is usually very different. The problem comes when trying to mix labels into arrays. The lack of sophistication in the TeX Notation plays against it here.

Moodle allows an easy adoption of tables to make it work though. For example:

 Bill the baker supplies three shops, A, B and C with pies, pasties and sausage rolls.
He is expected to determine the stock levels of those three shops in his estimation of supplies.


It is better to use the Moodle Fullscreen editor for this, to have a better idea of how the end product will look and to take advantage of the additional tools available. Design decisions need occupy our attention for a while. We need a table of five rows and four columns. The first row is a header row, so the label is centred. The next row needs four columns, a blank cell to start and labels A, B and C. The next three rows are divided into two columns, with the labels, pies, pasties and sausage rolls in each row of the first column and the matrix resides in a merged set of columns there. So first the table:

 Insert Table - initial properties Merge Cells Button Advanced Properties You may need to look into the Advanced properties setting of the tables and cells to make this work.

This is the immediate result:

While not a very good look, it can be made better by tweaking the table using the advanced settings and properties buttons and then you can tweak the matrix itself.

## Tweaking the Matrix

Things are not always as they seem, be aware, the "c" does not stand for "column", it actually stands for "centre". The columns are aligned by the letters l, for left, c for centre and r for right.

Each column is spread across 50 pixels, so the value of 50 is entered into the alignment declaration. The plus sign before the value is used to "propogate" or to force the value across the whole matrix, but is not used when wanting to separate only one column.

To set the rows is a little more problematic. The capital letter C sets the vertical alignment to the centre, (B is for baseline, but that does not guarantee that the numbers will appear on the base line, and there does not appear to be any third value). The plus sign and following value sets the height of all rows to the number given. In this I have given it a value of 25 pixels for the entire matrix. If there were four or five rows, the same height requirement is made.

The order things appear is also important. If you change the order of these settings, they will either not work at all, or will not render as you expect them to. If something does not work properly, then check to make sure you have the right order first.

The rule for performing operations on matrices is that they must be equal matrices. For example, addition matrices look like:

with the results obvious. The code is:

 $$\left[\begin{array}{c+50C+25.c.c} 11&14&12 \ \hdash16&12&22 \ \hdash 14&17&15 \end{array}\right] + \left[\begin{array}{c+50C+25.c.c} 60&60&60 \ \hdash 40&40&30 \ \hdash 30&30&30 \end{array}\right]$$


## A Subtraction Matrix

Similar to an addition matrix in its construction, the subtraction matrix is subject to the same rules of equality.

Using the same essential data, we can calculate the daily sales of each of the shops.

The code is:

 $$\left[\begin{array}{c+50C+25.c.c} 72&95&68 \ \hdash 54&61&65 \ \hdash 48&51&60 \end{array}\right] - \left[\begin{array}{c+50C+25.c.c} 11&14&12 \ \hdash 16&12&22 \ \hdash 14&17&15 \end{array}\right] = \left[\begin{array}{c+50C+25.c.c} 61&81&56 \ \hdash 38&49&43 \ \hdash 34&34&48 \end{array}\right]$$


This code looks more complex than it really is, it is cluttered by the lines and alignment sequences.

## Multiplication Matrices

Different than the addition or subtraction matrices, the multiplication matrix comes in three parts, the row matrix, the column matrix and the answer matrix. This implies it has a different construction methodology.

And the code for this is:

 $$\begin{array} 10&14&16\end{array} \ \left[\begin{array} 45 \\ 61 \\ 19 \end{array}\right] \ = \ \begin{array} 450&854&304\end{array}$$


While different, it is not necessarily more complex. For example a problem like:

 Bill the baker is selling his product to Con the cafe owner, who
wants to make sure his overall prices are profitable for himself.
Con needs to make sure that his average price is providing sufficient
profit to be able to keep the cafes open. Con makes his calculations
on a weekly basis, comparing cost to sale prices.


With the pies, pasties and sausage rolls in that order he applies them to the cost and sale price columns :

The code for this is:

 $$\left[\begin{array} 350&310&270 \end{array}\right] \ \left[\begin{array} \2.10&\3.60 \ \2.05&\3.60 \ \1.90&\3.10 \end{array} \right] \ = \ \left[\begin{array} \735.00&\1260.00 \ \635.50&\1116.00 \ \513.00&\837.00 \end{array}\right]$$