# LaTeX/C2/Equations/English

 Visual Cue Narration Opening slide Welcome to this tutorial on writing equations using LaTeX. My name is Kannan Moudgalya. Learning objectives slide Down arrow Down arrow Down arrow In this tutorial, we will learn How to create an equation in LaTeX. How to write multiple equations How to align multiple equations and Why we should avoid the dollar mode and blank lines while writing equations System requirements slide One may use any of Linux, Windows or the Mac operating system. One needs LaTeX. I shall use TexWorks, although it is not required. Prerequisites slide Press Down arrow Down arrow What are the prerequisites? One needs to be familiar with spoken tutorials that introduce LaTeX. Exposure to the recommended method of side-by-side learning. This information is available at the Spoken Tutorial webpage. Additional material slide I shall use the file equations.tex Open in TeXworks I have opened it in TeXworks. Back to slides file, press down arrow Press down arrow Press down arrow It is available as a code file along with this tutorial. You need to have it to practise along with me. If you don't have it, please download it from the Spoken Tutorial webpage. Slide on Leslie Lamport’s book I will next call your attention to this standard textbook by Leslie Lamport. I learnt my LaTeX from this book. It is available for about Rs. 500. Web browser is opened Let me show on the web browser where one can buy it. Let us begin this tutorial Open equations.tex Let us learn how to write equations using LaTeX. I have already opened the file equations.tex in TeXworks. I have saved it as numbers.tex to use in this tutorial. I will keep the file equations.tex intact, and not change it. Open numbers.tex Let me open numbers.tex Please pause the tutorial, make this copy and open it. Whenever you want to start afresh, you can make a new copy of equations.tex I recommend this method whenever a code file is given with ANY spoken tutorial. Press the Typeset key Let us compile this file by pressing the Typeset arrow at the top left hand corner. Pdf file You can see the pdf file on the right. Switch to the tex file. Let us look at the tex file, which begins with its usual commands. Highlight 8cm I have chosen the width of the pdf file to be 8cm. This is the only way I can show the entire file and also use a large font. Change 8 to 15 Put back 8 You may want to increase it to a more reasonable value, such as 15cm. But I will continue to use 8cm. Click amsmath line I am using the package amsmath. Click the first align I write the first equation within the align star environment, as shown here. Switch to the pdf and highlight the equation. You can see how it gets typeset in the pdf file. Click u(t) line in tex On the left hand side of this equation, we have u of t. Click u(t) in the pdf file On the right hand side, I have produced big square brackets. Hover on \left and click \right How did I do this? With back slash left square and back slash right square brackets as shown here. Scroll the tex file up Click align* line Similarly, I write a second equation using align star. Click the x_1 line On the left hand side, we have the derivative of a vector. Click on the eqn in the pdf file We can see the pdf output here. Click on matrix tex On the right hand side, we have a 3 by 3 matrix. Click on matrix pdf See the corresponding output. Delete row 1 compile Suppose we delete the first row in this matrix and compile. Click the pdf We get a 2 by 3 matrix pdf output. The first line is gone. It is your responsibility to make the equations correct and consistent. Undo the last command in tex Let me put the row back. Compile Let me compile. You can also add more rows, if necessary. Similarly, you can change the columns, too. Recall that we used the dollar mode to write formulae in another tutorial. Click on begin align in tex Here, align plays the role of the dollar mode. In fact, one should not put the dollar sign within the align environment. Put $and compile Suppose we put the alpha symbol within$ signs and compile. Error message We get an error message about dollar. Press red cross symbol to abort Press the cross symbol on the top left red box and abort the previous compilation. Remove \$ signs Let us remove the dollar sign. Compile again, it works! Below the line with alpha, leave a blank line Another common mistake is leaving blank lines in the align environment. Let me leave an empty line and compile. Error message It gives an error message. Put % If you need this gap, put %, the comment character, in the first column. Press red cross symbol to abort Abort compiling. Press Typeset symbol to compile Compile again - it compiles ok. So it is important to remember that you should not leave a blank line within the align statement. Remove the blank line Let me remove this line and compile. Next, I want to align the two equations by the equal to sign. For this, we need to put both equations inside one align star environment. Remove \end{align*} Remove \begin{align*} Remove the end align* command of the first equation. Remove the begin align* command of the second equation. Compile Let us compile. In the pdf file We see only one equation appearing. The text in between the two equations appears as a large string. The second equation does not even show up. This is not what we wanted. This problem is solved with the help of the intertext command. Add braces before and after the text. Let us put the text in between braces. Put the text into \intertext{} Let us also put this command, back slash intertext as I type now. Note that intertext is one word, without a space in between. Point to the \ Do not forget the back slash before intertext. Point to the closing brace Also, do not forget the closing brace. These are all common mistakes. Compile On compiling, we get this pdf file. You see both equations now. But unfortunately, you see both the equations right aligned. Not aligned by the equal to sign. So, I am not happy with it. I want to align by the equal to sign. Put & sign before = To do this, let us put the ampersand sign in front of the equal to sign. Let's do it for the first equation. Repeat in the 2nd eqn. And then let's do it for the second equation. If you have more equations to be aligned, do this for all of them. Compile On compiling, we see the two equations aligned by the equal to sign. The equations are aligned even though there is text in between. Remember to use the intertext command whether you want the equations aligned or not. Delete text lines What do we do if we don’t have text between equations? To understand this, let us delete the entire text between the two equations. Put \\ Note that we should not leave an empty line. Compile On compiling, we see both equations coming in the same line. We didn’t tell LaTeX to start the second equation in the next line. Add \\ We solve this by putting two back slashes at the end of the first equation. Compile Let us compile, to get the correct pdf file. Undo Let us now undo and put the text in between two equations. Compile Let us compile once more. This is where we will stop. Let me go to the slides. Summary slide Down arrow Down arrow This page summarises what we learnt in this tutorial. Please recall each of these commands. This is your first assignment. More assignments slide Down arrow I will give some more assignments. Can you pause the video and try to produce these equations? The required code is given here. Assignment 3 Can you produce these equations? Notice that these equations are now aligned at the equal to sign. Assignment 4 What happens if you forget a required ampersand sign? Please pause the video and try this input. You should get this output. Forgetting ampersand signs is a common mistake made by everyone! Assignment 5 Can you pause this video and try to produce this output? Use the hint given here. Assignment 6 In this assignment, you have to align three equations. Please pause the video here, and try to produce them by yourself. I have given the answer here. Assignment 7 I have the last assignment in this slide. Insert some text between equations. About the ST slide I will now give some general information. This video summarises the Spoken Tutorial project. Workshops slide We conduct workshops using Spoken Tutorials. Answers slide Press down arrow Down arrow Down arrow Down arrow Down arrow twice Do you have questions in THIS Spoken Tutorial? Please visit this site Choose the minute and second where you have the question Explain your question briefly Someone from our team will answer them You will have to register on this website to ask questions. Where to post slide For topics not covered in spoken tutorials, visit stack exchange at this address. Contact us slide For any other questions, please contact us. Acknowledgement slide Spoken Tutorial project is funded by MHRD, Government of India. Thanks for joining. Goodbye.