1. Feb 3, 2008

### jaime2000

I searched and it looked like no one had posted this before, so here it is. Trig without tears is an awesome site in which some guy explains trigonometry, from the basic functions of sine and cosine to the double and half angle identities. The interesting part is that the author, who believes it is wrong to use memorization as a substitute for thinking and disagrees with the memorization-based approach to identities regularly found in school, instead teaches you how to develop the identities in a way that is easy to follow and remember. I wish I had read this when I was taking pre-calculus last summer. It's great! ^.^

2. Apr 19, 2008

### soahamcauchy

thanks man...i feel trig is easy now

3. May 14, 2008

### DeanBH

Rofl.

IP check these guys £100 says that theyre the same person.

4. May 14, 2008

### cristo

Staff Emeritus
I'll PM you the address to send my £100 cheque to

5. Jul 28, 2008

### Herodotus

Love the approach

6. Sep 8, 2008

### physics_mania

Any more tips?

7. Sep 8, 2008

### physics_mania

Could you please give me another website, so I can have more of a reference point?

8. Sep 8, 2008

### physics_mania

Cristooooooo Any more tips?

9. Sep 8, 2008

### cristo

Staff Emeritus
Erm... I'm not sure what you mean!

10. Dec 13, 2009

### Greek2Me64

11. Mar 11, 2010

### physics_pupil

great work! trig is much more fun this way!

12. Aug 13, 2010

### QuarkCharmer

Wow thanks! That first link is pretty spiffy.

I actually enjoyed reading the first few pages of the OP's link as well. It seems perfectly informative to me.

13. Oct 7, 2010

### dougouk

hey, just wanted to say thanks.
Didn't really try out the site yet but I book marked it in plan for next sem.
Should help me in calculus right ^^

14. Nov 18, 2010

### dkotschessaa

Thanks for this resource. I finished my Algebra studies yesterday and I'm waiting for a trig book to come in the mail. This will serve in the meantime.

Only thing missing - I need some problems to solve! Can anybody help me out?

-DaveKA

15. Nov 18, 2010

### stevenb

A good trig identity tip is that if you ever run into trouble doing (or remembering) a trig identity, you can always fall back on the following two Euler relations.

$$\cos x ={{e^{i x}+e^{-i x}}\over{2}}$$

$$\sin x ={{e^{i x}-e^{-i x}}\over{2 i}}$$

where i is the square root of negative one.

For example, take the famous one,

$$\sin ^2 x+\cos ^2 x =1$$

plug in the relations and one gets

$${{(e^{i x}+e^{-i x})^2-(e^{i x}-e^{-i x})^2}\over{4}} =1$$

$${{(e^{2i x}+2+e^{-2i x})-(e^{2i x}-2+e^{-2i x})}\over{4}} =1$$

$${{4}\over{4}} =1$$

$$1 =1$$

Last edited by a moderator: Dec 3, 2010