document.write( "Question 735965: cos 4θ + 4 cos 2θ ≡ 8 cos4 θ − 3.
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Algebra.Com's Answer #449616 by mananth(16946) $\"\"$ $\"About$

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cos(4θ) =
\n" ); document.write( "cos(2*(2θ)) =
\n" ); document.write( "2cos^2(2θ) - 1 =
\n" ); document.write( " 2[ 2cos^2(θ) - 1 ]^2 - 1
\n" ); document.write( " 2 [ 4cos^4(θ) - 4cos^2(θ) + 1 ] - 1
\n" ); document.write( " 8cos^4(θ) - 8cos^2(θ) + 1.....................(1)\r
\n" ); document.write( "\n" ); document.write( ".............\r
\n" ); document.write( "\n" ); document.write( "4 cos 2theta\r
\n" ); document.write( "\n" ); document.write( "4(2 cos^2 $\"+Theta\"$ -1)\r
\n" ); document.write( "\n" ); document.write( "8 cos^2 $\"+theta\"$ -4................................(2)\r
\n" ); document.write( "\n" ); document.write( "(1)+(2)= RHS\r
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\n" ); document.write( "\n" ); document.write( "8cos^4(θ) - 8cos^2(θ) + 1 + 8 cos^2 $\"+theta\"$ -4= RHS\r
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