document.write( "Question 682713: How proof this?
\n" ); document.write( "1)4* cos ^4 x + 4* sin ^2 -3 = cos ^2 2X
\n" ); document.write( "2) cos ^4 - sin ^4X = cos 2X \n" ); document.write( "
Algebra.Com's Answer #423296 by solver91311(24713)\"\" \"About 
You can put this solution on YOUR website!
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\n" ); document.write( "\n" ); document.write( "You can't prove either one of those. x and X are two different things. In the first one you have a sine function with no argument. In the second one you have a cosine function with no argument.\r
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\n" ); document.write( "\n" ); document.write( "John
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\n" ); document.write( "Egw to Beta kai to Sigma
\n" ); document.write( "My calculator said it, I believe it, that settles it
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