document.write( "Question 767174: please prove that: sin^4 theta - cos^4 theta = 2sin^2 theta - 1. \n" ); document.write( "
Algebra.Com's Answer #467462 by Edwin McCravy(20060)\"\" \"About 
You can put this solution on YOUR website!
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document.write( "sin4(q) - cos4(q) = 2sin2(q) - 1\r\n" );
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document.write( "[sin2(q) - cos2(q)][sin2(q) + cos2(q)]\r\n" );
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document.write( "[sin2(q) - cos2(q)][1]\r\n" );
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document.write( "sin2(q) - cos2(q)\r\n" );
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document.write( "sin2(q) - [1 - sin2(q)]\r\n" );
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document.write( "sin2(q) - 1 + sin2(q)\r\n" );
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document.write( "2sin2(q) - 1\r\n" );
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document.write( "Edwin
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