document.write( "Question 1117819: Solve for all solutions, x, in degrees.\r
\n" ); document.write( "\n" ); document.write( " $\"cos%282x%29\"$ = $\"%281%2F2%29cos%28x%29\"$ \r
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Algebra.Com's Answer #732968 by stanbon(75887) $\"\"$ $\"About$

You can put this solution on YOUR website!
Solve for all solutions, x, in degrees.\r
\n" ); document.write( "\n" ); document.write( "cos(2x)=(1/2)cos(x)
\n" ); document.write( "2cos^2(x)-1 = (1/2)cos(x)
\n" ); document.write( "4cos^2(x)-2= cos(x)
\n" ); document.write( "4cos^2(x) - cos(x) - 2 = 0
\n" ); document.write( "------
\n" ); document.write( "cos(x) = [1+-sqrt(1-4*4*-2)]/8
\n" ); document.write( "cos(x) = [1+-sqrt(33)]/8
\n" ); document.write( "cos(x) = 0.8431 or cos(x) = -0.5931
\n" ); document.write( "x = arccos(0.8431) = 32.53 degrees
\n" ); document.write( "Or
\n" ); document.write( "x = arccos(-0.5931) = 126.38 degrees
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\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H.
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