- #1
Chewy0087
- 368
- 0
Homework Statement
express cos^4 x in terms of cos 4x and cos 2x given that
cos^ x = 0.5(1 + cos 2x)
The Attempt at a Solution
i did some playing around for a minute and came to this;
cos^4 x = 0.25 + (cos2x)/2 + (cos 4x +1)/8
and thought, great! now i'll just check it on wolfram however i got this;
http://www.wolframalpha.com/input/?i=y+=0.25+++(cos2x)/2+++(cos+4x++1)/8
as opposed to
http://www.wolframalpha.com/input/?i=cos+^4+x
now, just looking at the graphs it seems okay however none of the alternate forms or expansions are the same, i would love it if someone could just verify that I'm right it's quite an important question!
thanks again