document.write( "Question 1107872: How do I simplify \"cos%282x-pi%2F2%29\" using sum and difference identities? \n" ); document.write( "
Algebra.Com's Answer #722906 by ikleyn(52786)\"\" \"About 
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document.write( "First step is  TO LEARN  sum and difference identities.\r\n" );
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document.write( "See the lessons\r\n" );
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document.write( "    - FORMULAS FOR TRIGONOMETRIC FUNCTIONS\r\n" );
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document.write( "    - Addition and subtraction formulas\r\n" );
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document.write( "    - Addition and subtraction formulas - Examples\r\n" );
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document.write( "in this site.\r\n" );
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document.write( "Second step is to learn on how to apply them.\r\n" );
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document.write( "    a)  \"cos%282x-pi%2F2%29\" = \"cos%282x%29%2Acos%28pi%2F2%29+%2B+sin%282x%29%2Asin%28pi%2F2%29\" = cos(2x)*0 + sin(2x)*1 = sin(2x);\r\n" );
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document.write( "    b)  sin(2x) = sin(x+x) = sin(x)*cos(x) + cos(x)*sin(x) = 2*sin(x)*cos(x).\r\n" );
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document.write( "Answer.  \"cos%282x-pi%2F2%29\" = 2*sin(x)*cos(x).\r\n" );
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