document.write( "Question 677925: Solve for x in [0,2pi]:
\n" ); document.write( "cos 2x = -sin x \n" ); document.write( "

Algebra.Com's Answer #421186 by lwsshak3(11628) $\"\"$ $\"About$

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Solve for x in [0,2pi]:
\n" ); document.write( "cos 2x = -sin x
\n" ); document.write( "cos^2x-sin^2x=-sinx
\n" ); document.write( "1-sin^2x-sin^2x=-sinx
\n" ); document.write( "-2sin^2x+sinx+1=0
\n" ); document.write( "2sin^2x-sinx-1=0
\n" ); document.write( "(2sinx+1)(sinx-1)=0
\n" ); document.write( "..
\n" ); document.write( "2sinx+1=0
\n" ); document.write( "sinx=-1/2
\n" ); document.write( "x=7π/6, 11π/6 (in quadrants III and IV where sin<0)
\n" ); document.write( "and
\n" ); document.write( "sinx-1=0
\n" ); document.write( "sinx=1
\n" ); document.write( "x=π/2\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "

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