Line Segment Congruence :
Two line segments are congruent if and only if they have the same length or measure.
Angle Congruence :
Two angles are congruent if and only if they have the same measure.
Polygon Congruence :
Two polygons are congruent if and only if their corresponding sides and angles are congruent.
Linear Pair :
If two angles form a linear pair then they are supplementary.
Vertical Angle :
If two angles are vertical angles then they are congruent.
Lines :
If two parallel lines are cut by a transversal then the corresponding angles are congruent
Converse of Parallel Lines :
If two lines are cut by a transversal to form pairs of congruent corresponding angles then the lines are parallel.
Perpendicular Bisector :
If a point is on the perpendicular bisector of a line segment then the point is equidistant from the endpoints of the segment.
Converse of Perpendicular Bisector :
If a point is equidistant from the endpoints of a segment then it is on the perpendicular bisector of the segment.
Shortest Distance :
The shortest distance from a point to a line is measured along the perpendicular segment from the point to the line.
Angle Bisector :
If a point is on the bisector of an angle then the point is equidistant from both sides of the angle.
Centroid Existence :
The three medians of a triangle are concurrent at a point called the centroid.
Centroid Location :
For any given triangle the centroid is on the interior of the triangle.
Centroid Distance :
The centroid divides the median into two segments in such a way that the distance from the vertex to the centroid is twice the distance from the centroid to the midpoint.
Center of Gravity :
The centroid of a triangle is the center of gravity of the triangular region.
Orthocenter Existence :
The three altitudes of a triangle are concurrent at a point called the orthocenter.
Orthocenter Location:
If a triangle is acute then the orthocenter is in the interior region of the triangle.If a triangle is right then the orthocenter is the vertex of the right angle. If a triangle is obtuse then the orthocenter is on the outside of the triangle.
Orthocenter Distance :
The product of the parts into which the orthocenter divides an altitude is the equivalent for all three perpendiculars.
Circumcenter Existence :
The three perpendicular bisectors of a triangle are concurrent at a point called the circumcenter.
Circumcenter Location:
If a triangle is acute then the circumcenter is on the interior region of the triangle. If the triangle is right then the circumcenter is the midpoint of the hypotenuse. If the triangle is obtuse then the circumcenter is on the outside of the triangle.
Circumcenter Distance :
The circumcenter is equidistant from the vertices of a triangle.
Incenter Existence :
The three angles bisectors of a triangle are concurrent at a point called the incenter.
Incenter Location :
For any given triangle the incenter is on the interior of the triangle.
Incenter Distance :
The incenter is equidistant from the sides of a triangle.