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jtart2
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I'm verify some trigonometry equations and am confused about a couple of things. (This is self-study, I'm not in school)
The equation cos4x = 1+8cos^4-8cos^2 can be solved by re-writing as 2(cos2x)^2 -1 and factoring out which yields the correct answer, however based on what I've seen in other double angle identity equations one can re-write cos4x as cos(2x + 2x).
I believe this can be written as [(2cos^2 - 1)(2cos^2-1)] + [(2cos^2-1)(2cos^2-1)], however the answer then comes out to 8cos^4-8cos^2+2. So it's off by "+1".
What about my thinking is flawed? They can't both be correct!
Thanks for your help.
Joe
The equation cos4x = 1+8cos^4-8cos^2 can be solved by re-writing as 2(cos2x)^2 -1 and factoring out which yields the correct answer, however based on what I've seen in other double angle identity equations one can re-write cos4x as cos(2x + 2x).
I believe this can be written as [(2cos^2 - 1)(2cos^2-1)] + [(2cos^2-1)(2cos^2-1)], however the answer then comes out to 8cos^4-8cos^2+2. So it's off by "+1".
What about my thinking is flawed? They can't both be correct!
Thanks for your help.
Joe