You are not logged in.
#1 2006-01-08 09:46:35
- number0001
- Novice
Offline
Help--Another Trig Problem
I got another trig problem, which is to prove (make the left side of the "=" equal to the right side).
(cos3x-cosx)/(sin3x-sinx)=-tan2x
I tried it but got stuck. Thanks very much for any help!
#2 2006-01-08 10:00:11
- mikau
- Super Member
Offline
Re: Help--Another Trig Problem
I could work it out myself but I think you should.
First I'd suggest replacing cos(3x) and sin(3x) with cos(2x + x) and sin(2x + x) then use the sum identities. We did this in the previous example. And note the identity tan (2x) = (2 tan x)/(1 - tan^2 (x) ). Also note that tan x = (sin x)/(cos x)
You can do it!
A logarithm is just a misspelled algorithm.
#3 2006-01-08 10:03:08
- mikau
- Super Member
Offline
Re: Help--Another Trig Problem
Also note the identiy for sin(2x) and the three identities for cos(2x).
I'd really really really reccomend printing out a reference sheet of all the indentities. I have a binder of lots of difference indentities and math notes. This is math, not spelling. Understanding why a formula works is more important then remembering it. Just print out a reference sheet.
A logarithm is just a misspelled algorithm.