document.write( "Question 1063187: What would be the best next step for verifying the trig identity?\r
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Algebra.Com's Answer #678246 by Edwin McCravy(20060) $\"\"$ $\"About$

You can put this solution on YOUR website!

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document.write( "The \"C\" answer is really silly because it goes backward to the given identity.\r\n" );
document.write( "Notice that \"C\" is the same as the original given identity.\r\n" );
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document.write( "The \"D\" answer is wrong because it changes the left side cos²B-sin²B to -1. \r\n" );
document.write( "That's incorrect.  If the left side had been cos²B+sin²B or sin²B+cos²B that\r\n" );
document.write( "could be changed to 1. Or if it had been -cos²B-sin²B it could have been changed\r\n" );
document.write( "to -1.  The person who thinks \"D\" is correct is careless with signs.\r\n" );
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document.write( "The \"A\" answer makes the mistake of removing parentheses. When a parentheses is\r\n" );
document.write( "preceded by a minus sign or a negative sign, all the terms inside must change\r\n" );
document.write( "their signs.\r\n" );
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document.write( "The answer \"B\" is like answer \"A\" but it doesn't make the mistake that \"A\" makes.\r\n" );
document.write( "So it's the correct choice.\r\n" );
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document.write( "Edwin

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