I need help asap! 1+cos(8x)=?

Question

anonymous · Answer

@mathmale

anthony1914 · Answer

cos^2(4x) = (1 + cos(8x))/2 

So 1 + cos(8x) = 2cos^2(4x)

anonymous · Answer

4sin(2x)
4cos(2x)
2sin^2(4x)
2cos^2(4x)
@anthony1914 You gave me a different answer last time you were helping, do you really know what the answer is?

marcelie · Answer

:o ....

anonymous · Answer

@marcelie can you help me?

marcelie · Answer

been awhile havent seen this but ill look for some links

anonymous · Answer

Thanks, this is confusing ;-;

marcelie · Answer

http://www.geteasysolution.com/1+cos(8x)=

marcelie · Answer

theres a formula for that hmm..

marcelie · Answer

double angles ? http://www.freemathhelp.com/images/doubleangles.png

anonymous · Answer

My issue is that when I try to find the answer using a calculator it separates cosine as if each is a variable

anonymous · Answer

Thank you for the links, hopefully they have something :D

marcelie · Answer

sure np

daniel.ohearn1 · Answer

Remember that (cos(2x))^2 does not equal cos(4x)  

and 2(cos(2x)) does not equal cos(4x)   

For this problem (cos(8x)+1) does not need to be rewritten          
 
now if you had equal to something in an equation we could do some more work with it.

anonymous · Answer

I'm pretty sure it's 1+cos(8x)=2cos^2(4x)

daniel.ohearn1 · Answer

Are you solving for x then?  What are you trying to do?

anonymous · Answer

I have to find the equation that it is equal to.

anonymous · Answer

Trig identities are confusing

daniel.ohearn1 · Answer

It's a true identity...  What is confusing about it?

anonymous · Answer

I don't understand how to prove it

daniel.ohearn1 · Answer

subtract 1 from both sides and substitute    

You can try disproving it with any number x 

-inf<x<inf

anonymous · Answer

you need to prove that it is equal to what ?!!