SOLUTION: solve for the exact value of x where 0 greater than or equal to X and less than/equal to 2 pi. cos^2 x-1=0 I did the factoring and FOILing and The two answers I got were:

Question 206572: solve for the exact value of x where 0 greater than or equal to X and less than/equal to 2 pi.
cos^2 x-1=0
I did the factoring and FOILing and
The two answers I got were:
cosx=-1 cosx=1
x=pi x=0,2pi
According to my instructor cosx=1's answers are not completly correct. I dont see what the problem is since cos(0) and cos(2pi) both =1. Am I missing something here? Thank you for your help.
Answer by mickclns(59) (Show Source): You can put this solution on YOUR website!
I'd be interested in seeing your instructor's answer (please email me). It seems correct to me, too.
Things I can see:
You say "where 0 greater than or equal to X and less than/equal to 2 pi" by which I assume you mean although, strictly speaking, what you have written is which is meaningless or if it could be given meaning there would be no solution possible because there is no x such that 0 greater than or equal to x and (x is) less than/equal to 2 pi.
Another possibility, the span usually given in problems such as this is . So I would check to see whether the second really includes the =. If so, maybe the instructor intended it not to have the = so 2pi would not be an answer. So take another look and ask again.
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