document.write( "Question 860396: Find to the nearest degree, the acute angle of rotation 1 that eliminates the xy term of -3x^2 + 3xy + 5y^2 - x + 2y - 6 = 0 \n" ); document.write( "

Algebra.Com's Answer #518415 by Edwin McCravy(20064) $\"\"$ $\"About$

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document.write( "The other tutor gave you an obtuse angle, not an acute angle.\r\n" );
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document.write( "The angle of rotation  of the graph \r\n" );
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document.write( "Ax² + Bxy + Cy² + Dx + Ey + F = 0\r\n" );
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document.write( "necessary to transform it into an equation in x' and y' which contains\r\n" );
document.write( "no term in x'y'\r\n" );
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document.write( "is calculated by  or  if A = C\r\n" );
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document.write( "Your equation is\r\n" );
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document.write( "-3x² + 3xy + 5y² - x + 2y - 6 = 0\r\n" );
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document.write( "In this case A=-3, B=3, C=5, D=-1, E=2, F = -6\r\n" );
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document.write( "Find the reference angle for ,\r\n" );
document.write( "using the inverse tangent function of a\r\n" );
document.write( "calculator using . That gives\r\n" );
document.write( "reference angle for  as 20.55604522\r\n" );
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document.write( "So the smallest positive value for \r\n" );
document.write( "that has tangent  is in QII, and is\r\n" );
document.write( "180-20.55604522 = 159.4439548\r\n" );
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document.write( "So\r\n" );
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document.write( "and\r\n" );
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document.write( "To nearest degree, 80°\r\n" );
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document.write( "Edwin

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