document.write( "Question 585136: What is 2cos^2 θ + cosθ -1=0 using the interval 0 ≤ θ < 2 π?
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Algebra.Com's Answer #373150 by lwsshak3(11628) $\"\"$ $\"About$

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What is 2cos^2 θ + cosθ -1=0 using the interval 0 ≤ θ < 2 π?
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\n" ); document.write( "2cos^2 θ + cosθ -1=0
\n" ); document.write( "(2cosθ+1)(cosθ-1)=0
\n" ); document.write( "2cosθ+1=0
\n" ); document.write( "2cosθ=-1
\n" ); document.write( "cosθ=-1/2
\n" ); document.write( "θ=2π/3 and 4π/3 (in quadrants II and III where cos<0)
\n" ); document.write( "or
\n" ); document.write( "cosθ-1=0
\n" ); document.write( "cosθ=1
\n" ); document.write( "θ=0
\n" ); document.write( "ans:
\n" ); document.write( "θ=0, 2π/3, and 4π/3 \n" ); document.write( "

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