
The Circumcenter of a triangle
Latin: circum  "around" centrum  "center"
Try this Drag the orange dots on each vertex
to reshape the triangle. Note the way the three perpendicular bisectors always meet at a point  the circumcenter
One of several centers the triangle can have, the circumcenter is the point where the
perpendicular
bisectors of a triangle intersect.
The circumcenter is also the center of the triangle's circumcircle 
the circle that passes through all three of the triangle's vertices. As you reshape the triangle above, notice that the circumcenter may lie
outside the triangle.
Special case  right triangles
In the special case of a right triangle, the circumcenter (C in the figure at right) lies exactly at the midpoint of the hypotenuse (longest side).
See also Circumcircle of a triangle.
Finding the circumcenter
It is possible to find the circumcenter of a triangle using construction techniques using a compass and straightedge.
See Construction of the Circumcircle of a Triangle has an animated demonstration of the technique,
and a worksheet to try it yourself. The circumcenter is found as a step to constructing the circumcircle.
Summary of triangle centers
There are many types of triangle centers. Below are four of the most common.
In the case of an equilateral triangle,
all four of the above centers occur at the same point.
The Euler line  an interesting fact
It turns out that the orthocenter, centroid, and circumcenter of any triangle are
collinear
 that is,
they always lie on the same straight line called the Euler line, named after its discoverer.
For more, and an interactive demonstration see Euler line definition.
Other triangle topics
General
Perimeter / Area
Triangle types
Triangle centers
Congruence and Similarity
Solving triangles
Triangle quizzes and exercises
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