Is Khan Academy enough? Trig for Calculus

For the discussion of math. Duh.

Moderators: gmalivuk, Moderators General, Prelates

Posts: 12
Joined: Sun Jan 23, 2011 2:13 am UTC

Is Khan Academy enough? Trig for Calculus

Hi it's me again,

Here is my situation. I dropped out of calculus because I had problems with algebra. I had taken it and trig over two years ago with a crummy teacher blah blah etc. So I retook college algebra for a refresher. Now I feel pretty confident in my algebra skills. I was the same with trig as well until I found Khan Academy.

My question is this: Is the Trigonomety playlist from khanacademy.org sufficient to get me through calculus?

Assuming that I understand all of it. I've watched up to the "Fun Trig Problem" video and have understood it all. I love khanacademy, best thing since indoor plumbing.

Edit: A second question: Is Khan thorough enough on all the math playlists? From what I've seen in the algebra section he is.

Tirian
Posts: 1891
Joined: Fri Feb 15, 2008 6:03 pm UTC

Re: Is Khan Academy enough? Trig for Calculus

Probably. No reason you can't go through the Khan Academy's calculus lessons and see for yourself.

Yesila
Posts: 221
Joined: Sun Dec 16, 2007 11:38 am UTC

Re: Is Khan Academy enough? Trig for Calculus

In my opinion what you need trig-wise for calculus is to be familiar enough with it that when you see it you don't freak out and think it's hard. When you see it you need to think "Oh right trig stuff. I can do that."

That being said the other things you should "know" are:

What the graphs of the trig functions look like and what their values are at multiples of pi/6 and pi/4 (so in degrees, 0,30,45,60,90 etc)
Spoiler:
in particular the angles that produce, zeros, ones or that are undefined should be recalled with very little thought and the other ones you should be able to recognize that you know 'should know' the answer and if it takes you a bit of time to remember at what angle(s) cosine has a value of /sqrt{3}/2 fine -- you look at it, notice you should know the answer, realize an answer is not at 0, or pi, quickly throw out pi/4, ponder pi/6 and pi/3 (maybe even pi/5) for a bit recall the graph and realize that pi/6 is one of the solutions you are looking for. At that recalling the graph can allow you to easily find all the other answers as well.

The "definitions" of the trig functions.
Spoiler:
By definitions I really mean you need to know how ratios of side lengths in right triangles relate to trig functions. And you also need to know how to rewrite all the other trig functions in terms of quotients of sines and cosines (and/or the number one).

You should know that trig identities exist and have some idea of what they look like.
Spoiler:
Ideally you have at least a few of them memorized. Pythagorean being the main one.

There are (many) more trig identities out there than any "normal" person can ever expect to know, but you'll find only a handful (10-20) of them typically show up in your calc class -- these are often pointed out on the front or back inside cover of your book, they are also the ones that your teacher will use repeatedly in example problems on the board... and that you see in your homework. If you don't have the "important" ones memorized already you'll find yourself "accidentally" memorizing them if you pay attention and do your homework.

For completeness I'll mention the law or sines and the law of cosines... but their use will vary greatly depending on your calc class. Some classes will use them lots... others sparsely and still others not at all.
Spoiler:
As with the trig identities if you find your teaching using them in class, and assigning homework with them... then make sure you know them and how to use them. If they don't use them, then just be able to recognize what they look like so when you see one (or the need for one) you can go look it up again.

By the way I like Kahn academy. Especially for people that took a course a few years ago, and have forgotten half of it, and are rusty on most of the rest of it. These people aren't ready to take the next class but its a waste of time to retake the whole class. Kahn academy allows those students to relearn the 1 or 2 (or 3,4 or 5) specific topics they need help on in a few days or weeks, instead of having to sludge through a whole 16 week course to pick up the 8 days worth of material you can't remember.

Posts: 12
Joined: Sun Jan 23, 2011 2:13 am UTC

Re: Is Khan Academy enough? Trig for Calculus

And you also need to know how to rewrite all the other trig functions in terms of quotients of sines and cosines (and/or the number one).

Now that I haven't covered yet. I'm assuming it's just simple memorization though.

Thank you. That was exactly what I was looking for. I wish I had known about Khan back when I had trouble with algebra.

Edit: Oh and FYI, there is a fundraiser for Khan going on right now here:http://www.crowdrise.com/Khanacademyproject/fundraiser/WIRED