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3.4 out of 5 stars
CK-12 Trigonometry
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32 of 32 people found the following review helpful
This is a very approachable and well presented introductory text on Trigonometry. It is written with a high school student in mind, but it can be used by anyone who is unfamiliar with this subject. It covers all the traditional topics in a trigonometry course - functions, triangles, angles, etc. The material is presented in a very straightforward manner and it is very easy to follow. There are multiple worked-out examples throughout the text, and each section ends with a several problems and their solutions. The problems vary in difficulty, and many are designed with practical applications in mind. The book also emphasizes the use of scientific calculator in working out of many problems, which is pedagogically a good approach. This book is available under the Creative Commons License through the CK-12 foundation, which means it can be reprinted, modified and resold if necessary.

The Kindle formatting of this textbook leaves something to be desired. The book was originally typeset in LaTeX, and this did not translate all that smoothly into the Kindle format. I've found that getting this textbook on other e-readers or computers in the epub format rendered it much more satisfactorily.

This is not the flashiest textbook that you will come across, but in my opinion it gets the job done.
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15 of 16 people found the following review helpful
The ck12.org foundation has made more than a dozen free math and science textbooks available, and this geometry textbook is one of them.

There are full images in this. This book is much larger than what is typically available for free. The images look good, but they are typically roughly two times too large at the moment. Also, all places where TeX is used, a too-large blocky image is used instead. For example, "(3,3)" is presented three times larger than the surrounding text. There are many of these on every page. In this particular ebook, it's inconsistently sized. For example, see location 4561-71.

Not all images seem to have made it. For example, on location 4513-28, three images are listed as "not available". Since this is a digital textbook, I'm sure those will be fixed. The errors above will also probably be addressed quickly.

Despite the above mentioned (and perhaps soon-fixed) flaws, this is worthwhile download.
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9 of 9 people found the following review helpful
on December 27, 2012
This little free book suffices for someone already well versed in math and confident in themselves to review Trig, but I would Never suggest anyone use it to actually learn the subject. I can forgive the occasional typographical error that slips past a proofreader, but to allow errors such as the area of a rectangle being "2*w*h", and then compound that error by using the formula over and over is a deathknell for any textbook. Not only does it teach how to solve the question wrong but it undermines any confidence in the rest of the book since whenever the student comes up with a different answer they won't know who is wrong: them or the book.
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6 of 6 people found the following review helpful
TOP 1000 REVIEWERVINE VOICEon November 29, 2010
It's been over 20 years since I've had a trigonometry class and I've forgotten a great deal of math over the years, so when I found a free trigonometry book available on the Kindle, I grabbed it and wanted to check it out. Granted, it will probably never have a practical use in my day job, but it never hurts to read and glance over it.

The book layout isn't that great. The Kindle formatting isn't that great either. For example, the Table of Contents is located at the end of the book, so if you start at the beginning of the book, you're a little confused as to the aims for the first chapter.

So why 5 stars? If you're a student, this book is worth downloading. If I was retaking a University math course, I'd download it to have as a second reference source. And it's free.
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5 of 5 people found the following review helpful
on January 4, 2013
I realize that it's free, but seriously! The area of a rectangle does not equal 2hw! And there are not 360 seconds in a degree! (A=wh, a second=1/3600 of a degree)That's as far as I've gotten in the book, I'm sure I'll find more as my exploration deepens, but these are INEXCUSEABLE! I haven't taken a math course in 5 years, I've forgotten most of what I learned, which is why I was looking for a cheap refresher, but this is ridiculous. I'm smarter than my math book.
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4 of 4 people found the following review helpful
on June 14, 2011
This review is for the Kindle edition. The text and layout of trigonometry is well presented and methodical. The problem come with presenting it on Kindle. It's hard to put a protractor on the screen (heaven forbid you also try to use a compass). Some presentations just plain belong on paper. Kindle is great for many things, but trig and geometry are not two of them.
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1 of 1 people found the following review helpful
on November 8, 2013
First of all, this text is very 1990ish in it's approach to the subject; you're better off with a 1960's approach as you will avoid the poor "goals" approach.
It's likely the poorest trigonometry text I've ever seen. The errors mentioned in the earlier 1-star reviews are just the beginning; I gave up after the lengthy "how-to" example involving the TI graphing calculator. I am at location 277 on the Kindle so a lot is still to follow.
My first major concern resulted in the discussion of the Domain of the function: f(x) = 1/x. The authors concluded that the Domain is {all reals except x not equal to zero}. "Except... not equal to..." is a double negative which results "in equals". So the authors have determined a Domain containing the only Real number not in the actual Domain.
I, too discovered the Contents being at the end of the text as I usually begin by taking my Kindle to the cover and table of contents. Imagine my shock when I turned the page after viewing the Contents and finding myself 100% through the book. So much for the goals.
If you want an excellent no-frills text on Trigonometry try to find Trigonometry by Heiniman (??). It's 1950ish and only about 140 pages long. It's short because it doesn't use the functions approach; it discusses trigonometry. If you want a discussion of function vs relation get a book on them. Trigonometry is a relatively simple concept that doesn't need intrusions to cloud the topic. Worry about < and > after you understand =.
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1 of 1 people found the following review helpful
on June 5, 2011
I may soon take a graduate level advanced math class so I need to do a quick brush up. I was going to start with calculus but then I saw this free book and decided to start simple. Sort of simple - in high school I skipped trig for calculus and started college in calculus so I never had trig - in some ways this would be new to me.

The book was clear and easy to understand. The style and language reflected the target audience - I quickly got back into the high-school-math-book mode though with a few things have changed in the last xx years since I was in school- up to date references/examples, URLs given in a few spots (high school for me was pre-Internet), many sections on using graphing calculators, etc.

For the most part I have no issues with the content or the way it was presented. I was a little taken aback the first time I came upon a section on using a graphing calculator but I guess you teach the kids what they'll be using. No, it wasn't that: my main problem is with the Kindle implementation.

The problem is that most of the equations are images. OK, most of the images are fine. In fact, pretty good. It's just that it seems they tried to fit multiple lines worth of equations onto 1 line and it often came out unreadable.

The first thing I did was turn my Kindle sideways. This helped but I was still missing quite a bit. I then tried the PC version. Even better yet I was still missing a lot.

In a few places I was missing main parts of the content, in which case I just found it on line. Trig is trig. More often how the concept was derived was unreadable. I could work it out on my own without a problem: I mean this is high school math and not rocket science. Worse yet are the answers to the questions, which are largely unreadable or, just as often, totally missing ("image not available" - this only happen with answers to problems and not the main text).

Of course when I say "this isn't rocket science" I'm referring to myself: I understand it could be to the target audience. This is a text book aimed at high school kids, not a review for a middle-aged mathematician (by degree, not occupation). It isn't fair to them to have so much of the book unreadable. They need all of the text, every equation, clearly legible to ensure they get the material.

As a supplement this is pretty good, particularly considering the price (or lack there-of). Or it can be used in a taught class if the instructor provides the missing material. Maybe even as a review for an old hand at math like me. For a primary book, particularly for a first time trigonometry student and/or a self-study student this cannot be recommended.
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I will use this both on my Kindle and on my PC with the purchase of CK-12 Trigonometry in a Kindle digital format, you can easily download the Kindle Reader for PCs and make the best of this book. It presents Trigonometry to the reader in a concise way to give the student an easy understanding of the subject. I think the review by Dr. Bogan Tunguz is probably all you need to read concerning this book, other than the fact the Kindle Reader for PC's allows you to read and study this book on your PC and your Kindle Reader. The combination is a winner if you choose the PC Reader App. and download it free from Amazon, then just open this, or any of your Kindle books on your PC.
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on March 11, 2014
I like this stuff. Not much for the every day life; however, ... . I gave it four stars! Why not get your own copy!
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