<PRE><B>Question 860523</B>
Find, to the nearest degree, the acute angle of rotation x that eliminates the xy term of -3x^2 + 3xy + 5y^2 - x + 2y - 6 = 0.
Form: Ax^2 + Bxy + Cy^2 + Dx + Ey + F = 0
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cot(2t) = (A-C)/B
cot(2t) = (-3-5)/3 = -8/3
tan(2t) = -3/8
2t = arctan(-5/8) = 170.56
t = 85.28 degrees
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Cheers,
Stan H.


a-41 degrees
b-80
c-81
d-40
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