Geometry: Theorems
Terms
Centroid
-
The point in a triangle at which the medians of a triangle intersect.
Circumcenter
-
The point at which the perpendicular bisectors
of a triangle intersect.
Concurrent
-
Intersecting at one point; lines, rays, segments, etc. are concurrent when they
intersect at one point.
External Segment
-
The segment contained by a secant segment with an endpoint on the circle and
at the fixed point outside the circle whose points all lie outside the circle
(except the endpoint on the circle).
Incircle
-
The point in a triangle at which the angle
bisectors of a triangle intersect. This point
is also the center of a circle inscribed in the triangle.
Inscribed Angle
-
An angle whose vertex lies on a circle and whose sides are contained by secant
lines.
Internal Segment
-
The segment contained by a secant segment whose endpoints are both on the
circle.
Isosceles Trapezoid
-
A trapezoid with congruent legs.
Lower Base Angles
-
The angles in an isosceles trapezoid whose vertices are the endpoints of the
longer base.
Median of a Triangle
-
A segment within a triangle with one endpoint at a vertex of the triangle and
the other endpoint at the midpoint of the side opposite the vertex. Every
triangle has three medians.
Midsegment
-
A segment within a triangle whose endpoints are midpoints of the sides of the
triangle. Every triangle has three midsegments.
Orthocenter
-
The point at which the altitudes of a triangle
intersect.
Point of Concurrency
-
The intersection point of concurrent lines, segments, etc.
Remote Interior Angles
-
The two angles of a triangle that are not adjacent to the exterior angle which
is drawn by extending one of the sides.
Secant Segment
-
A segment with one endpoint on a circle, the other endpoint at a fixed point
outside the circle, and one point of intersection with the circle, not including
its endpoint.
Theorem
-
A statement about geometric figures that has been proved in the past, and can be
accepted as a truth in the present without proof. A list of important theorem's
can be found in review.
Upper Base Angles
-
The two angles of an isosceles trapezoid whose vertices are the endpoints of
the smaller base.
