document.write( "Question 924330: Please solve the following equation.
\n" ); document.write( "(Enter your answers as a comma-separated list. Let k be any integer. Enter DNE is there is no solution.)
\n" ); document.write( "2 cos 2θ − 1 = 0
\n" ); document.write( "(a) Find all solutions of the equation.
\n" ); document.write( "θ = \r
\n" ); document.write( "\n" ); document.write( "(b) Find the solutions in the interval [0, 2π).
\n" ); document.write( "θ = \r
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Algebra.Com's Answer #560765 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
Part a)\r
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\n" ); document.write( "\n" ); document.write( "Solve for \"theta\"\r
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\n" ); document.write( "\n" ); document.write( "\"2%2Acos%282theta%29-1+=+0\"\r
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\n" ); document.write( "\n" ); document.write( "\"2%2Acos%282theta%29=+1\"\r
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\n" ); document.write( "\n" ); document.write( "\"cos%282theta%29=+1%2F2\"\r
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\n" ); document.write( "\n" ); document.write( "\"2theta=+arccos%281%2F2%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"2theta=+pi%2F3%2B2pi%2Ak\" or \"2theta=+-pi%2F3%2B2pi%2Ak\" where k is any integer.\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+%281%2F2%29%2A%28pi%2F3%2B2pi%2Ak%29\" or \"theta=+%281%2F2%29%2A%28-pi%2F3%2B2pi%2Ak%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+pi%2F6%2Bpi%2Ak\" or \"theta=+-pi%2F6%2Bpi%2Ak\"\r
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\n" ); document.write( "\n" ); document.write( "The general solutions are \"theta=+pi%2F6%2Bpi%2Ak\" or \"theta=+-pi%2F6%2Bpi%2Ak\" where k is any integer.\r
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\n" ); document.write( "\n" ); document.write( "You can condense that into one equation: \"theta=+%22%22%2B-pi%2F6%2Bpi%2Ak\" (take note of the plus/minus)\r
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\n" ); document.write( "\n" ); document.write( "Part b)\r
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\n" ); document.write( "\n" ); document.write( "We'll find the first set of solutions.\r
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\n" ); document.write( "\n" ); document.write( "Plug in integer values of k into \"theta=+pi%2F6%2Bpi%2Ak\" to generate solutions. Make sure you are between \"x+=+0\" and \"x+=+2pi+=+6.28\" roughly.\r
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\n" ); document.write( "\n" ); document.write( "Plug in \"k+=++0\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+pi%2F6%2Bpi%2Ak\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+pi%2F6%2Bpi%2A0\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+pi%2F6\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+0.5235987755983\"\r
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\n" ); document.write( "\n" ); document.write( "This is in the interval [0,2pi), so we keep it.\r
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\n" ); document.write( "\n" ); document.write( "Plug in \"k+=++1\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+pi%2F6%2Bpi%2Ak\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+pi%2F6%2Bpi%2A1\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+pi%2F6%2Bpi\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+7pi%2F6\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+3.6651914291881\"\r
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\n" ); document.write( "\n" ); document.write( "This is in the interval [0,2pi), so we keep it.\r
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\n" ); document.write( "\n" ); document.write( "Plug in \"k+=++2\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+pi%2F6%2Bpi%2Ak\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+pi%2F6%2Bpi%2A2\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+6.8067840827779\"\r
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\n" ); document.write( "\n" ); document.write( "we have gone over 6.28, so we stop here and we don't include this solution because it is not in the interval [0,2pi)\r
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\n" ); document.write( "\n" ); document.write( "Now we move onto the second part.\r
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\n" ); document.write( "\n" ); document.write( "Plug in integer values of k into \"theta=+-pi%2F6%2Bpi%2Ak\" to generate solutions. Make sure you are between \"x+=+0\" and \"x+=+2pi+=+6.28\" roughly.\r
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\n" ); document.write( "\n" ); document.write( "Plug in \"k+=++0\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+-pi%2F6%2Bpi%2Ak\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+-pi%2F6%2Bpi%2A0\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+-0.5235987755983\"\r
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\n" ); document.write( "\n" ); document.write( "That is less than x = 0, so we toss out this solution.\r
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\n" ); document.write( "\n" ); document.write( "Plug in \"k+=++1\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+-pi%2F6%2Bpi%2Ak\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+-pi%2F6%2Bpi%2A1\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+-pi%2F6%2Bpi\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+5pi%2F6\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+2.6179938779915\"\r
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\n" ); document.write( "\n" ); document.write( "This is in the interval [0,2pi), so we keep it.\r
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\n" ); document.write( "\n" ); document.write( "Plug in \"k+=++2\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+-pi%2F6%2Bpi%2Ak\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+-pi%2F6%2Bpi%2A2\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+-pi%2F6%2B2pi\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+11pi%2F6\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+5.7595865315813\"\r
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\n" ); document.write( "\n" ); document.write( "This is in the interval [0,2pi), so we keep it.\r
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\n" ); document.write( "\n" ); document.write( "Plug in \"k+=++3\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+-pi%2F6%2Bpi%2Ak\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+-pi%2F6%2Bpi%2A3\"\r
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\n" ); document.write( "\n" ); document.write( "\"theta=+8.9011791851711\"\r
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\n" ); document.write( "\n" ); document.write( "we have gone over 6.28, so we stop here and we don't include this solution because it is not in the interval [0,2pi)\r
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\n" ); document.write( "\n" ); document.write( "The exact solutions to part b) are \"x+=+pi%2F6\", \"x+=+7pi%2F6\", \"x+=+5pi%2F6\", \"x+=+11pi%2F6\". They are exact solutions in terms of \"pi\"\r
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\n" ); document.write( "\n" ); document.write( "Let me know if that helps or not. Thanks.\r
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\n" ); document.write( "\n" ); document.write( "If you need more help, feel free to email me at jim_thompson5910@hotmail.com\r
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\n" ); document.write( "\n" ); document.write( "My Website: http://www.freewebs.com/jimthompson5910/home.html
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