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Thread: coordinates of intersection for polar curves

  1. #1
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    coordinates of intersection for polar curves

    I have r =2 and r=3+2sintheta

    --> 2=3+2sintheta
    ---> sintheta = -1/2

    theta = 4pi/3 , 11pi/6

    coordinates (4pi/3,2), (11pi/6,2)

    Did i do something wrong?
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    Re: coordinates of intersection for polar curves

    Quote Originally Posted by lc99 View Post
    I have r =2 and r=3+2sintheta

    --> 2=3+2sintheta
    ---> sintheta = -1/2

    theta = 4pi/3 , 11pi/6

    coordinates (4pi/3,2), (11pi/6,2)

    Did i do something wrong?
    Actually it should be points in the form $\displaystyle (r, ~ \theta )$, not $\displaystyle ( \theta, ~ r)$.

    I'm getting $\displaystyle sin( \theta) = -1/2 \implies \theta = -\frac{\pi}{6} + \pi = \frac{5 \pi}{6} \text{ and } \theta = -\frac{\pi}{6} + 2 \pi = \frac{11 \pi}{6}$

    -Dan
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    Re: coordinates of intersection for polar curves

    would 5pi/6 give positive value?
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  4. #4
    Forum Admin topsquark's Avatar
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    Re: coordinates of intersection for polar curves

    Quote Originally Posted by lc99 View Post
    would 5pi/6 give positive value?
    Whoops! I was thinking of cosine I should have said $\displaystyle \frac{\pi}{6} + \pi = \frac{ 7 \pi}{6}$. The other angle I listed is correct.

    Thanks for the catch.

    -Dan
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