document.write( "Question 1136950: A is an obtuse angle such that cos(A)=-4/5. Find:\r
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Algebra.Com's Answer #754794 by Edwin McCravy(20056)\"\" \"About 
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A is an obtuse angle such that cos(A)=-4/5. Find:\r
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document.write( "A is a QII angle.  We draw a 3-4-5 right triangle in QII.\r\n" );
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document.write( "\"cos%28A%29=x%2Fr=%28-4%29%2F5=-4%2F5\", \"sin%28A%29=y%2Fr=3%2F5\",\r\n" );
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document.write( "\"cos%282A%29=2cos%5E2%28A%29-1=2%28-4%2F5%29%5E2-1=2%2816%2F25%29-1=32%2F25-25%2F25=7%2F25\"\r\n" );
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document.write( "\"sin%282A%29=2sin%28A%29cos%28A%29=2%283%2F5%29%28-4%2F5%29=-24%2F25\"\r\n" );
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document.write( "\"sin%284A%29=2sin%282A%29cos%282A%29=2%28-24%2F25%29%287%2F25%29=-336%2F625\"\r\n" );
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document.write( "Edwin
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