document.write( "Question 1104466: Prove the identity:\r
\n" ); document.write( "\n" ); document.write( "cos^2 y - sin^2 y = 1-2sin^2 y \n" ); document.write( "

Algebra.Com's Answer #719206 by ikleyn(52793) $\"\"$ $\"About$

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\n" ); document.write( "Prove the identity:\r
\n" ); document.write( "\n" ); document.write( "cos^2(y) - sin^2(y) = 1 - 2sin^2(y).
\n" ); document.write( "~~~~~~~~~~~~~~~~~\r
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document.write( "  cos^2(y) - sin^2(y) =      (substitute here cos^2(y) = 1 - sin^2(y) to get) \r\n" );
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document.write( "= 1 - 2*sin^2(y).\r\n" );
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\n" ); document.write( "\n" ); document.write( "QED.\r
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