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Math Help - Rotations and systems of equatoins

  1. #1
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    Rotations and systems of equatoins

    I was searching on google and discovered this forum, so I figure you guys could help me understand this.
    The question is to rotate x^2-10xy+y^2+1=0 I understand most of the rotating aspect except for finding theta. The step cot 2(theta)=A-C/B. How do I know what quadrant I should be looking in? When I plug in that equation the result is cot 2(theta)=0 But I dont understand how 2(theta)=pi/2 when it could also equal 3pi/2. Help please
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  2. #2
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    Quote Originally Posted by deeartist View Post
    I was searching on google and discovered this forum, so I figure you guys could help me understand this.
    The question is to rotate x^2-10xy+y^2+1=0 I understand most of the rotating aspect except for finding theta. The step cot 2(theta)=A-C/B. How do I know what quadrant I should be looking in? When I plug in that equation the result is cot 2(theta)=0 But I dont understand how 2(theta)=pi/2 when it could also equal 3pi/2. Help please
    Have you tried rotating using:
    1. pi/4
    2. 3pi/4?

    What do you notice?
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  3. #3
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    Oh so your saying that you can only rotate using the first quadrant?
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