**TI83F* AppVariable file 03/21/07, 14:46 GLGE05nav 9AE51D1EC13445C5B24A00CF0B737DCFGLGE05.GLGE051  altitude!~altitude:A line segment perpendicular to the base of a figure with endpoints on the base and on the vertex opposite the base. centroid of a triangle!centroid of a triangle:The point of intersection of the three medians of a triangle. In the figure, X is the centroid of triangle JKM.  circumcenterTcircumcenter:The point of concurrency of the perpendicular bisectors of a triangle.  concurrent!concurrent:Three or more lines or segments that meet at a common point. In the figure, seg. JR, seg. KP, and seg. MQ are concurrent. incenterHincenter:The point of concurrency of the angle bisectors of a triangle. &indirect proof (or indirect reasoning)Jindirect proof (or indirect reasoning):In an indirect proof, one assumes that the statement to be proved is false. One then uses logical reasoning to deduce that a statement contradicts a postulate, theorem, or one of the assumptions. Once a contradiction is obtained, one concludes that the statement assumed false must be true. median of a triangle!median of a triangle:A segment in which one endpoint is the vertex of a triangle and the other endpoint is the midpoint of the side opposite that vertex.  orthocenterEorthocenter:The point of concurrency of the altitudes of a triangle.  perpendicular bisectord !vperpendicular bisector:A segment that is perpendicular to another segment and passes through that segment's midpoint.8`0HxHH ( ɍ&PI)*`9I)*@8@06QP@0 @@   @@ @0 @@@       8$$$88`0HHH0|p |@`~` 0 ? b!0A )A 0 (0 P`8` 0)ecbHVU(x"dU(HCRbTH@,"*lAL(`(( Fl @ @@@00 ? @    8`0HxHK?@@ @0    0 0 0  0" 0  z