simple trigonometry problem

bloody-orc

New Member

• Apr 16, 2007

• #1

cos(2*x)+cos(4*x) = cos(x);

How to solve this...
It's too late and i just cant figure it out...
i know x should = 1/2 Pi. but cant figure out how the hell to get that

 

Papabravo

Well-Known Member

• Apr 16, 2007

• #2

Since the identity is not generally true, but only true for a particular value it reduces upon substitution to:

+1 + (-1) = 0

There is no general method that I know of for solving this kind of problem since it involves transcendental functions.

 

bloody-orc

New Member

• Apr 17, 2007

• #3

you and your American math knowledge
it's is very much possible to do it (now I see, what my classmate meant, when she went to America as an exchange student. here she couldn't understand anything, but there oh... she was a genius in class (and school).

anyway this is one way of solving this: **broken link removed**

or this one: **broken link removed**

 

Last edited: Apr 17, 2007

Papabravo

Well-Known Member

• Apr 17, 2007

• #4

Truly, Estonians like Elbonians have dizzying intellects!

 

ericgibbs

Well-Known Member

Most Helpful Member

• Apr 17, 2007

• #5

hi,

I know papabravo dosn't need me to back him up, BUT the solution to your
problem did come from a States side web source!

Give credit, where credit is due.

Regards.

 

bloody-orc

New Member

• Apr 17, 2007

• #6

the solutions were uploaded by me... freewebtown just gives me space to post my intelligence And my remarks were not to offend anyone. especially Americans. You have much better university system than we do (yours just costs 450 000$ more). All they teach us is theory, but there it's all the other way around. more practical things and less "jibba-jabba"

 

Papabravo

Well-Known Member

• Apr 17, 2007

• #7

I was by no means offended, but I also don't feel stronly motivated to check your results. I'll be happy to stipulate that they are completely beyond my graduate level mathematics background. Like I said, you have a truly dizzying intellect. My head is still spinning. I am reminded of a particularly pedantic problem on my fresshman calculus exam.

Code:

Take the derivative of
 
y = tan(x) ^ tan(x) ;

In an engineering career spanning 40 years I've never found a use for that one.

 

Last edited: Apr 17, 2007