document.write( "Question 1075523: Cos(2x)+cosx=0 \n" ); document.write( "

Algebra.Com's Answer #690158 by Boreal(15235) $\"\"$ $\"About$

You can put this solution on YOUR website!
2 cos^2 x-1=cos 2x
\n" ); document.write( "2 cos^2x-1+cos x=0
\n" ); document.write( "rewrite as 2 cos^2 x+cos x-1=0
\n" ); document.write( "(2 cos x-1)(cos x+1)=0
\n" ); document.write( "cos x=1/2
\n" ); document.write( "cos x=-1
\n" ); document.write( "This works at pi, pi/3 and 5pi/3
\n" ); document.write( " $\"graph%28300%2C300%2C-6%2C6%2C-2%2C2%2Ccos%282x%29%2Bcos%28x%29%29\"$ \n" ); document.write( "

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