Calculation help.....

jimmy11

Hey lads

can anyone direct me in the right way with solving this

(cosh2x - cos2x) (cosh2x+ cos2x)
x = 2

I cant remember how its done at all bein a while

cheers

breadmonkey

You can just blast it through the calculator. Definitions of coshx and sinhx here:

http://en.wikipedia.org/wiki/Hyperbolic_cosine

jimmy11

to be honest my maths are brutal its bein years

i havin a clue just need this solved or shown how to

mawk

x ~~ 0.610372761461925
or so my phone tells me.

do you need to do it manually for any good reason?

bnt

For starters, the question is in the form (x-y)(x+y), which has certain algebraic implications that may or may not help:

(x-y)(x+y) = x²-y²

.

I'm assuming that the value of x is in Radians, not Degrees, which means I get an answer wildly different to mawk's when I use Excel's functions. If you use the standard derivations of cosh(x) as detailed on that Wikipedia page, you must use Radians.

jimmy11

cheers thanks lads

mawk

hmm, ill admit that i didnt actually give a tenth of a seconds thought to the content of the question, just copypasted it straight into wolfram alpha on my phone (reading on boards mobile) which looking at the answer probably took it as:
((cosh2x - cos2x) (cosh2x+ cos2x)(x)) = 2

fixing the input and assuming radians gives this:
http://www.wolframalpha.com/input/?i=1%2F2+%28cosh%284+x%29-cos%284+x%29%29+%3D+1%2F2+%28cosh%288%29-cos%288%29%29&a=TrigRD_R

+-2