Wikipedia
Search Wikipedia:

Latest topics
» How do leavening agents make dough rise?
Thu May 11, 2017 2:42 am by bejoy

» Solvent effects on chemical reaction
Thu May 11, 2017 2:41 am by bejoy

» How does salt lower the freezing point of water?
Thu May 11, 2017 2:16 am by bejoy

» Benedict’s reagent test for Monosaccharides
Thu May 11, 2017 2:06 am by bejoy

» Industrial Production of Diethyl Ether
Thu May 11, 2017 2:04 am by bejoy

» How to prepare sodium acetate at home?
Thu May 11, 2017 1:59 am by bejoy

» Production of ethyl acetate by esterification
Tue Jan 10, 2017 5:06 am by bejoy

» Toluene biodegration using jet loop reactor
Mon Jan 09, 2017 6:41 am by bejoy

» Making of ammonia by Haber’s process
Mon Jan 09, 2017 6:15 am by bejoy

June 2017
MonTueWedThuFriSatSun
   1234
567891011
12131415161718
19202122232425
2627282930  

Calendar Calendar

Free Hit Counter

pheta, cos2pheta = 4cospheta, uncomplicated trig

View previous topic View next topic Go down

pheta, cos2pheta = 4cospheta, uncomplicated trig

Post  karooomph on Sun Feb 08, 2009 9:59 am

What is the sum of the values of θ between 0 and 2π inclusive satisfying cos2θ = cos4θ?


Last edited by karooomph on Sun Feb 08, 2009 9:02 pm; edited 2 times in total
avatar
karooomph

Posts : 74
Join date : 2008-11-19
Age : 22
Location : ubseikastan

View user profile

Back to top Go down

Re: pheta, cos2pheta = 4cospheta, uncomplicated trig

Post  bfrsoccer on Sun Feb 08, 2009 1:20 pm

Although maybe you can use some trig identities to help you from the start in this problem, I think you would do something like:

1. cos2θ = cos4θ
1. Let some variable, like v, equal 2θ: cos v=cos(2v)
2. My TI-89 Titanium tells me that cos(2v)=2(cos v)^2-1, so: cos v=2(cos v)^2-1
3. Then, you can make another substitution and let w=cos v, and you end up with a quadratic equation: 2w^2-w-1=0
4. Solve for w, which will will then let you solve for values of v between 0 and 4pi (because v=2θ, and θ goes from 0 to 2pi), which then gives you values for θ, I think, which you can then add up

I think funion987 knows more about trig identities and stuff so he may have a better way of solving this problem.
avatar
bfrsoccer
Administrator

Posts : 61
Join date : 2008-11-09

View user profile

Back to top Go down

Re: pheta, cos2pheta = 4cospheta, uncomplicated trig

Post  karooomph on Sun Feb 08, 2009 3:53 pm

alrite, thanks bfr
avatar
karooomph

Posts : 74
Join date : 2008-11-19
Age : 22
Location : ubseikastan

View user profile

Back to top Go down

Term Papers

Post  monti on Wed Apr 28, 2010 6:33 am

It's great to see fresh, creative ideas that have never been done before.

Term Papers

monti

Posts : 10
Join date : 2010-04-28

View user profile

Back to top Go down

Re: pheta, cos2pheta = 4cospheta, uncomplicated trig

Post  Sponsored content


Sponsored content


Back to top Go down

View previous topic View next topic Back to top


 
Permissions in this forum:
You cannot reply to topics in this forum