The angle between two tilted circles












0














Two-Part Question:



1.) Two circles (C1 and C2) sit tangent to both each other, and to the space between an inner circle C3 and an outer circle C4. If r1 and r2 are known, how do we find theta?



Circle Problem



2.) Can this problem be "generalized" so that instead of the smaller circles occupying the space between C3 and C4, they lie in the space between two concentric ellipses? Or, is that a different problem entirely?



Thank you!










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    0














    Two-Part Question:



    1.) Two circles (C1 and C2) sit tangent to both each other, and to the space between an inner circle C3 and an outer circle C4. If r1 and r2 are known, how do we find theta?



    Circle Problem



    2.) Can this problem be "generalized" so that instead of the smaller circles occupying the space between C3 and C4, they lie in the space between two concentric ellipses? Or, is that a different problem entirely?



    Thank you!










    share|cite|improve this question

























      0












      0








      0







      Two-Part Question:



      1.) Two circles (C1 and C2) sit tangent to both each other, and to the space between an inner circle C3 and an outer circle C4. If r1 and r2 are known, how do we find theta?



      Circle Problem



      2.) Can this problem be "generalized" so that instead of the smaller circles occupying the space between C3 and C4, they lie in the space between two concentric ellipses? Or, is that a different problem entirely?



      Thank you!










      share|cite|improve this question













      Two-Part Question:



      1.) Two circles (C1 and C2) sit tangent to both each other, and to the space between an inner circle C3 and an outer circle C4. If r1 and r2 are known, how do we find theta?



      Circle Problem



      2.) Can this problem be "generalized" so that instead of the smaller circles occupying the space between C3 and C4, they lie in the space between two concentric ellipses? Or, is that a different problem entirely?



      Thank you!







      geometry






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      share|cite|improve this question











      share|cite|improve this question




      share|cite|improve this question










      asked Dec 3 '18 at 20:56









      kreeser1

      10110




      10110






















          1 Answer
          1






          active

          oldest

          votes


















          3














          Hint:



          the centers of $C_1$ and $C_2$ are at a distance from the center of the great circle :
          $$
          r_3=r_1+left(frac{r_2-r_1}{2} right)=r_2-left(frac{r_2-r_1}{2} right)
          $$





          enter image description here



          $APE$ is a rectangular triangle with $angle EAP=theta/2$ and we know $AE=r_3$ and $EP=r_3-r_1$. And we have: $sin (theta/2)=frac{EP}{EA}$






          share|cite|improve this answer























          • Thank you for the comment. Should your comment be that the centers of C1 and C2 are at a distance from the center of the great circle: r3 = r2 - ((r2 - r1)/2)?
            – kreeser1
            Dec 3 '18 at 21:26










          • Yes, sorry for the typo. I edit.:)
            – Emilio Novati
            Dec 3 '18 at 21:59










          • Thank you Emilio. I still do not understand how to solve the problem, but I will keep your comment in mind. I appreciate your input!
            – kreeser1
            Dec 3 '18 at 22:01










          • I added a figure.
            – Emilio Novati
            Dec 3 '18 at 22:18










          • Thank you Emilio, I understand now. Not sure why I couldn't see that before when you added your first hint.
            – kreeser1
            Dec 3 '18 at 22:26











          Your Answer





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          1 Answer
          1






          active

          oldest

          votes








          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          3














          Hint:



          the centers of $C_1$ and $C_2$ are at a distance from the center of the great circle :
          $$
          r_3=r_1+left(frac{r_2-r_1}{2} right)=r_2-left(frac{r_2-r_1}{2} right)
          $$





          enter image description here



          $APE$ is a rectangular triangle with $angle EAP=theta/2$ and we know $AE=r_3$ and $EP=r_3-r_1$. And we have: $sin (theta/2)=frac{EP}{EA}$






          share|cite|improve this answer























          • Thank you for the comment. Should your comment be that the centers of C1 and C2 are at a distance from the center of the great circle: r3 = r2 - ((r2 - r1)/2)?
            – kreeser1
            Dec 3 '18 at 21:26










          • Yes, sorry for the typo. I edit.:)
            – Emilio Novati
            Dec 3 '18 at 21:59










          • Thank you Emilio. I still do not understand how to solve the problem, but I will keep your comment in mind. I appreciate your input!
            – kreeser1
            Dec 3 '18 at 22:01










          • I added a figure.
            – Emilio Novati
            Dec 3 '18 at 22:18










          • Thank you Emilio, I understand now. Not sure why I couldn't see that before when you added your first hint.
            – kreeser1
            Dec 3 '18 at 22:26
















          3














          Hint:



          the centers of $C_1$ and $C_2$ are at a distance from the center of the great circle :
          $$
          r_3=r_1+left(frac{r_2-r_1}{2} right)=r_2-left(frac{r_2-r_1}{2} right)
          $$





          enter image description here



          $APE$ is a rectangular triangle with $angle EAP=theta/2$ and we know $AE=r_3$ and $EP=r_3-r_1$. And we have: $sin (theta/2)=frac{EP}{EA}$






          share|cite|improve this answer























          • Thank you for the comment. Should your comment be that the centers of C1 and C2 are at a distance from the center of the great circle: r3 = r2 - ((r2 - r1)/2)?
            – kreeser1
            Dec 3 '18 at 21:26










          • Yes, sorry for the typo. I edit.:)
            – Emilio Novati
            Dec 3 '18 at 21:59










          • Thank you Emilio. I still do not understand how to solve the problem, but I will keep your comment in mind. I appreciate your input!
            – kreeser1
            Dec 3 '18 at 22:01










          • I added a figure.
            – Emilio Novati
            Dec 3 '18 at 22:18










          • Thank you Emilio, I understand now. Not sure why I couldn't see that before when you added your first hint.
            – kreeser1
            Dec 3 '18 at 22:26














          3












          3








          3






          Hint:



          the centers of $C_1$ and $C_2$ are at a distance from the center of the great circle :
          $$
          r_3=r_1+left(frac{r_2-r_1}{2} right)=r_2-left(frac{r_2-r_1}{2} right)
          $$





          enter image description here



          $APE$ is a rectangular triangle with $angle EAP=theta/2$ and we know $AE=r_3$ and $EP=r_3-r_1$. And we have: $sin (theta/2)=frac{EP}{EA}$






          share|cite|improve this answer














          Hint:



          the centers of $C_1$ and $C_2$ are at a distance from the center of the great circle :
          $$
          r_3=r_1+left(frac{r_2-r_1}{2} right)=r_2-left(frac{r_2-r_1}{2} right)
          $$





          enter image description here



          $APE$ is a rectangular triangle with $angle EAP=theta/2$ and we know $AE=r_3$ and $EP=r_3-r_1$. And we have: $sin (theta/2)=frac{EP}{EA}$







          share|cite|improve this answer














          share|cite|improve this answer



          share|cite|improve this answer








          edited Dec 3 '18 at 22:24

























          answered Dec 3 '18 at 21:00









          Emilio Novati

          51.5k43472




          51.5k43472












          • Thank you for the comment. Should your comment be that the centers of C1 and C2 are at a distance from the center of the great circle: r3 = r2 - ((r2 - r1)/2)?
            – kreeser1
            Dec 3 '18 at 21:26










          • Yes, sorry for the typo. I edit.:)
            – Emilio Novati
            Dec 3 '18 at 21:59










          • Thank you Emilio. I still do not understand how to solve the problem, but I will keep your comment in mind. I appreciate your input!
            – kreeser1
            Dec 3 '18 at 22:01










          • I added a figure.
            – Emilio Novati
            Dec 3 '18 at 22:18










          • Thank you Emilio, I understand now. Not sure why I couldn't see that before when you added your first hint.
            – kreeser1
            Dec 3 '18 at 22:26


















          • Thank you for the comment. Should your comment be that the centers of C1 and C2 are at a distance from the center of the great circle: r3 = r2 - ((r2 - r1)/2)?
            – kreeser1
            Dec 3 '18 at 21:26










          • Yes, sorry for the typo. I edit.:)
            – Emilio Novati
            Dec 3 '18 at 21:59










          • Thank you Emilio. I still do not understand how to solve the problem, but I will keep your comment in mind. I appreciate your input!
            – kreeser1
            Dec 3 '18 at 22:01










          • I added a figure.
            – Emilio Novati
            Dec 3 '18 at 22:18










          • Thank you Emilio, I understand now. Not sure why I couldn't see that before when you added your first hint.
            – kreeser1
            Dec 3 '18 at 22:26
















          Thank you for the comment. Should your comment be that the centers of C1 and C2 are at a distance from the center of the great circle: r3 = r2 - ((r2 - r1)/2)?
          – kreeser1
          Dec 3 '18 at 21:26




          Thank you for the comment. Should your comment be that the centers of C1 and C2 are at a distance from the center of the great circle: r3 = r2 - ((r2 - r1)/2)?
          – kreeser1
          Dec 3 '18 at 21:26












          Yes, sorry for the typo. I edit.:)
          – Emilio Novati
          Dec 3 '18 at 21:59




          Yes, sorry for the typo. I edit.:)
          – Emilio Novati
          Dec 3 '18 at 21:59












          Thank you Emilio. I still do not understand how to solve the problem, but I will keep your comment in mind. I appreciate your input!
          – kreeser1
          Dec 3 '18 at 22:01




          Thank you Emilio. I still do not understand how to solve the problem, but I will keep your comment in mind. I appreciate your input!
          – kreeser1
          Dec 3 '18 at 22:01












          I added a figure.
          – Emilio Novati
          Dec 3 '18 at 22:18




          I added a figure.
          – Emilio Novati
          Dec 3 '18 at 22:18












          Thank you Emilio, I understand now. Not sure why I couldn't see that before when you added your first hint.
          – kreeser1
          Dec 3 '18 at 22:26




          Thank you Emilio, I understand now. Not sure why I couldn't see that before when you added your first hint.
          – kreeser1
          Dec 3 '18 at 22:26


















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