<PRE><B>Question 860396</B>
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
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Form:: Ax^2 +Bxy + Cy^2 + Dx + Ey + F = 0
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Angle of rotation:: cot(2t) = (A-C)/B = (-3-5)/3 = -8/3
2t = arc(tan(-3/8)) = -20.56 = 339.44
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Ans: t = 169.72
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Cheers,
Stan H.</PRE>