document.write( "Question 870190: Prove the identity
\n" ); document.write( "a) sin^4 x - cos^4 x = 1 0 2cos^2 x
\n" ); document.write( "Can you please help me ? Thanks so much in advance:) \n" ); document.write( "

Algebra.Com's Answer #524776 by mananth(16946) $\"\"$ $\"About$

You can put this solution on YOUR website!
$\"sin%5E4+%28x%29+-+cos%5E4+%28x%29+=+1+-+2cos%5E2+%28x+%29\"$ \r
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\n" ); document.write( "\n" ); document.write( " $\"%28sin%5E2%28x%29%2Bcos%5E2%28x%29%29%2A%28sin%5E2%28x%29-cos%5E2%28x%29%29\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"%281%29%281-cos%5E2%28x%29-cos%5E2%28x%29%29\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"1-2cos%5E2%28x%29\"$ \r
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