draw a line parallel to line
EF intersecting line AB at R and line
AC at Q. Let P be the intersection of
lines EF and CB. Prove that the
circumcircle of ⊿PQR passes through
the midpoint M of side BC.
Circumcircle of a triangle From Latin: circum- "around"
A circle which passes through all three vertices of a triangle
Also "Circumscribed circle".
Try this Drag the orange dots on each vertex to reshape the triangle. Note that the circumcircle always passes through all three points.
The circumcircle always passes through all three vertices of a triangle. Its center is at the point where all the perpendicular bisectors of the triangle's sides meet. This center is called the circumcenter. See circumcenter of a triangle for more about this.
Note that the center of the circle can be inside or outside of the triangle. Adjust the triangle above and try to obtain these cases.
The radius of the circumcircle is also called the triangle's circumradius.