document.write( "Question 206572: solve for the exact value of x where 0 greater than or equal to X and less than/equal to 2 pi.\r
\n" ); document.write( "\n" ); document.write( "cos^2 x-1=0\r
\n" ); document.write( "\n" ); document.write( "I did the factoring and FOILing and\r
\n" ); document.write( "\n" ); document.write( "The two answers I got were:\r
\n" ); document.write( "\n" ); document.write( "cosx=-1 cosx=1
\n" ); document.write( "x=pi x=0,2pi\r
\n" ); document.write( "\n" ); document.write( "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. \n" ); document.write( "

Algebra.Com's Answer #156300 by mickclns(59) $\"\"$ $\"About$

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. \r
\n" ); document.write( "\n" ); document.write( "Things I can see:
\n" ); document.write( "You say \"where 0 greater than or equal to X and less than/equal to 2 pi\" by which I assume you mean $\"0%3C=x%3C=2pi\"$ although, strictly speaking, what you have written is $\"0%3E=x%3C=2pi\"$ 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.\r
\n" ); document.write( "\n" ); document.write( "Another possibility, the span usually given in problems such as this is $\"0%3C=x%3C2pi\"$ . 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. \n" ); document.write( "

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