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Math Help - Can I get help with this triq problem?

  1. #1
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    Can I get help with this triq problem?

    I'm trying to find X P( x, -2/7)

    x^2+ -2/7=1 then I get
    x^2+ (-2/7)^2=1
    Than I get x^2=1-4/49=  x^2= \frac{49} {49}- \frac{4}{49}=\frac{45} {49} Then you get x=\sqrt \frac{45} {49}The answer is suppose to be  x=+ or -\sqrt{5}.

    How do you get  x= + - \sqrt{5}

    Thanks

    Jason
    Last edited by Darkhrse99; June 9th 2008 at 05:08 PM.
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  2. #2
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    Quote Originally Posted by Darkhrse99 View Post
    I'm trying to find X P( x, -2/7)

    x^2+ -2/7=1 then I get
    x^2+ (-2/7)^2=1
    Than I get [tex]x^2=1-4/49=  x^2= 49/49-4/49=x^2=45/49 The answer is suppose to be[tex] x=\sqrt{5}.

    How do you get sqrt + - 5?

    Thanks

    Jason
    Can I just be the first to say

    Huh?

    You started with
    x^2 \pm \frac{2}{7} = 1

    and went to
    x^2 + \left ( -\frac{2}{7} \right )^2 = 1

    How did you go from the first to the second step? The first does not imply the second.

    What exactly is it you are trying to find? "X P (x, -2/7)" makes no sense to me.

    -Dan
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  3. #3
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    Sorry for the confusion, the math code is kicking my butt.

    I'm trying to find point X on the unit circle.

    The book gave me the Y cord of \frac {-2} {7} . I need to find X.

    The formula  x^2+ y^2 =1 is used to find the answer.

    I plugged in  x^2 + \frac {-2} {7}squared=1

    Than I get x^2=1-\frac{4} {49} next I get x^2= \frac{49} {49}- \frac{4}{49}=\frac{45} {49} Then you get x=\sqrt \frac{45} {49}The answer is suppose to be  x=+ or -\sqrt{5}.
    Last edited by Darkhrse99; June 9th 2008 at 05:49 PM.
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  4. #4
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    I found the answer. The book was wrong. The answer is 3\sqrt{5}/7
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  5. #5
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by Darkhrse99 View Post
    Sorry for the confusion, the math code is kicking my butt.

    I'm trying to find point X on the unit circle.

    The book gave me the Y cord of \frac {-2} {7} . I need to find X.

    The formula  x^2+ y^2 =1 is used to find the answer.

    I plugged in  x^2 + \frac {-2} {7}squared=1

    Than I get x^2=1-\frac{4} {49} next I get x^2= \frac{49} {49}- \frac{4}{49}=\frac{45} {49} Then you get x=\sqrt \frac{45} {49}The answer is suppose to be  x=+ or -\sqrt{5}.
    The solution is
    \pm \frac{3 \sqrt{5}}{7}
    so your given answer was wrong. You did it (mostly) right.

    -Dan
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  6. #6
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    Yes, mostly right. I was stumped all day. The solutions manual said \pm\sqrt{5} but the text book said <br />
\pm \frac{3 \sqrt{5}}{7}<br />
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