document.write( "Question 321758: if $\"COS%28A%2BB%29%2ASIN%28C%2BD%29\"$ $\"%22=%22\"$ $\"COS%28A-B%29%2ASIN%28C-D%29\"$ ,SHOW THAT $\"COT%28A%29%2ACOT%28B%29%2ACOT%28C%29\"$ $\"%22=%22\"$ $\"COT%28D%29\"$ \n" ); document.write( "

Algebra.Com's Answer #230383 by Edwin McCravy(20062) $\"\"$ $\"About$

You can put this solution on YOUR website!
$\"cos%28A%2BB%29sin%28C%2BD%29\"$ $\"%22=%22\"$ $\"cos%28A-B%29sin%28C-D%29\"$
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Using well known formulas:\r\n" );
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document.write( "Using \"FOIL\" on both sides:\r\n" );
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document.write( "(Notice that it took two lines to write that equation because it was so long!\r\n" );
document.write( "The left side, then the equal sign, then the right side.)\r\n" );
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document.write( "The first terms on each side are the same, so they cancel.\r\n" );
document.write( "The last terms on each side are also the same so they cancel:\r\n" );
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document.write( "So all we have left is this:\r\n" );
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document.write( "Add the opposites of both negative terms to both sides and we end up with:\r\n" );
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document.write( "Divide both sides by 2\r\n" );
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document.write( "Divide both sides by ,\r\n" );
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document.write( "Cancel what will cancel:\r\n" );
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document.write( "Regroup the factors on the left:\r\n" );
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document.write( "Use the identity  and you end up\r\n" );
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document.write( "Edwin

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