Difference between revisions of "Nine point circle"

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Also known as '''Euler's circle''' or '''Feuerbach's circle''', as its name introduces itself that the nine point [[circle]] goes through nine [[point]]s, which are a given [[triangle]] <math>\triangle ABC</math>'s feet of [[altitude]] dropped from three [[vertex | vertices]] <math>A,B,</math> and <math>C</math>, usually denoted as <math>H_A,H_B,H_C</math>, and [[midpoint]]s of three [[side]]s, as <math>M_A,M_B,M_C</math>, and three [[Euler point]]s <math>E_A,E_B,E_C</math>.
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The '''nine point circle''' (also known as ''Euler's circle'' or ''Feuerbach's circle'') of a given [[triangle]] is a circle which passes through 9 "significant" points:
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  * The three feet of the [[altitude]]s of the triangle.
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  * The three [[midpoint]]s of the [[edge]]s of the triangle.
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  * The three midpoints of the segments joining the [[vertex | vertices]] of the triangle to its [[orthocenter]].  (These points are sometimes known as the [[Euler point]]s of the triangle.)
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That such a circle exists is a non-trivial theorem of [[Euclidean geometry]].
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The center of the nine point circle is the [[nine-point center]] and is usually denoted <math>N</math>.
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Revision as of 11:45, 6 July 2007

The nine point circle (also known as Euler's circle or Feuerbach's circle) of a given triangle is a circle which passes through 9 "significant" points:

 * The three feet of the altitudes of the triangle.
 * The three midpoints of the edges of the triangle.
 * The three midpoints of the segments joining the  vertices of the triangle to its orthocenter.  (These points are sometimes known as the Euler points of the triangle.)

That such a circle exists is a non-trivial theorem of Euclidean geometry.

The center of the nine point circle is the nine-point center and is usually denoted $N$.

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