- #1
Ackbach
Gold Member
MHB
- 4,155
- 89
Here is this week's POTW:
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A circle is in the plane with center at $O_a$ and some radius $r_a$. Another circle, not touching the first circle anywhere, has center at $O_b$ and some radius $r_b$. Points $A$ and $B$ are both (arbitrary) points on circle $A$ and circle $B$ respectively. Finally, Point $C$ is in such a location that $ABC$ is an equilateral triangle. Points $A$ and $B$ begin rotating in the same direction (say, counterclockwise) around their respective circles with the same angular speed (say, $\omega$) about their centers. During this process, point $C$ moves so that $ABC$ remains an equilateral triangle.
Prove that point $C$ is moving in a circle with same direction (counterclockwise) and angular speed ($\omega$) about some center $O_c$ somewhere in the plane.
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Remember to read the http://www.mathhelpboards.com/showthread.php?772-Problem-of-the-Week-%28POTW%29-Procedure-and-Guidelines to find out how to http://www.mathhelpboards.com/forms.php?do=form&fid=2!
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A circle is in the plane with center at $O_a$ and some radius $r_a$. Another circle, not touching the first circle anywhere, has center at $O_b$ and some radius $r_b$. Points $A$ and $B$ are both (arbitrary) points on circle $A$ and circle $B$ respectively. Finally, Point $C$ is in such a location that $ABC$ is an equilateral triangle. Points $A$ and $B$ begin rotating in the same direction (say, counterclockwise) around their respective circles with the same angular speed (say, $\omega$) about their centers. During this process, point $C$ moves so that $ABC$ remains an equilateral triangle.
Prove that point $C$ is moving in a circle with same direction (counterclockwise) and angular speed ($\omega$) about some center $O_c$ somewhere in the plane.
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Remember to read the http://www.mathhelpboards.com/showthread.php?772-Problem-of-the-Week-%28POTW%29-Procedure-and-Guidelines to find out how to http://www.mathhelpboards.com/forms.php?do=form&fid=2!