document.write( "Question 1204746: Rewrite the product as a sum or difference.
\n" ); document.write( "2 sin(9x) cos(2x) \n" ); document.write( "
Algebra.Com's Answer #841203 by ikleyn(52864)\"\" \"About 
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\n" ); document.write( "Rewrite the product as a sum or difference.
\n" ); document.write( "2 sin(9x) cos(2x)
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document.write( "Use a general formula\r\n" );
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document.write( "    sin(a)*cos(b) = \"%281%2F2%29%2A%28sin%28a-b%29+%2B+sin%28a%2Bb%29%29\",\r\n" );
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document.write( "which is valid for any angles \"a\" and \"b\".\r\n" );
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document.write( "In out case, a = 9x, b = 2x.  Therefore\r\n" );
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document.write( "    2*sin(9x)*cos(2x) = sin(9x-2x) + sin(9x+2x) = sin(7x) + sin(11x).    ANSWER\r\n" );
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\n" ); document.write( "\n" ); document.write( "About these formulas, see your textbook on Trigonometry or the lessons\r
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\n" ); document.write( "\n" ); document.write( "https://www.algebra.com/algebra/homework/Trigonometry-basics/Addition-and-subtraction-formulas-Examples.lesson\r
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