| A | B |
|---|
| collinear points | points that lie on the same line |
| non-collinear points | points that don't lie on the same line |
| coplanar | objects which lie on the same plane |
| non-coplanar | objects which don't lie on the same plane |
| postulate | statement that we accept without proof |
| theorem | statement that we can prove using logic |
| point | the intersection of two lines |
| line | the intersection of two planes |
| parallel lines | two coplanar lines that don't intersect |
| segment | two points and all points between them |
| congruent segments | segments with equal lengths |
| midpoint | point that divides a segment into two congruent segments |
| segment bisector | object that divides a segment into two congruent segments |
| ray | a part of a line that has only one endpoint |
| opposite rays | rays with the same endpoint which together form a line |
| angle | two rays joined by a common endpoint |
| vertex | common endpoint of two rays that form an angle |
| acute angle | angle with measure less than 90 degrees |
| right angle | angle with measure exactly 90 degrees |
| obtuse angle | angle with measure between 90 degrees and 180 degrees |
| straight angle | angle with measure exactly 180 degrees |
| angle bisector | object (such as a ray or line) which divides an angle into two congruent angles |
| degree | a unit to measure angles which equals a fraction (1/360th) of a circle |
| 90 degrees | the number of degrees in one-fourth of a circle |
| 180 degrees | the number of degrees in one-half of a circle |
| 360 degrees | the number of degrees in a circle |
| congruent angles | angles whose measures are equal |
| adjacent angles | coplanar angles with a common vertex and side, but no common interior points |
| complementary angles | a pair of angles whose measures add to 90 degrees |
| complements | a pair of angles whose measures add to 90 degrees |
| supplementary angles | a pair of angles whose measures add to 180 degrees |
| supplements | a pair of angles whose measures add to 180 degrees |
| linear pair | a pair of supplementary and adjacent angles |
| vertical angles | a pair of opposite angles formed by a pair of intersecting lines |
| vertical angles | a pair of angles whose sides form opposite rays |
| conditional statement | a statement that can be written in the form, "if p, then q." |
| hypothesis | the given information: part of a conditional statement found immediately after the word if |
| conclusion | the conclusion or result of the hypothesis: part of a conditional statement found immediately after the word then |
| counterexample | example showing a statement is not ALWAYS true, and is therefore false |
| converse | statement obtained from a conditional statement by switching the hypothesis and the conclusion |
| inverse | statement obtained from a conditional statement by negating the hypothesis and the conclusion |
| contrapositive | statement obtained from a conditional statement by negating AND switching the hypothesis and conclusion |
| biconditional statement | statement combining a conditional statement with its converse using the phrase "if and only if" |
| Venn Diagram | a diagram with two or more overlapping circles, used to show relationships between sets. |
| Law of Detachment | If p --> q is a true conditional and p is true, then q is true. |
| Law of Syllogism | If p --> q and q --> r are true conditionals, then p --> r is true. |
| intersecting lines | lines that have a point in common |
| parallel lines | coplanar lines that do not intersect. |
| perpendicular lines | lines that intersect at a |
| skew lines | lines that are non-coplanar and do not intersect |
| oblique lines | lines that intersect but are not perpendicular |
| slope | The steepness of a line expressed as a ratio, using any two points on the line |
| transversal | a line that intersects two other lines |
| corresponding angles | a pair of angles, both in the same position relative to two lines crossed by a transversal (that is, upper right, etc) |
| alternate interior angles | a pair of angles, both between two parallel lines and on opposite sides of the transversal |
| alternate exterior angles | a pair of angles, both exterior to two parallel lines and on opposite sides of the transversal |
| consecutive interior angles | a pair of angles, both between two parallel lines and on the same side of the transversal |
| polygon | a closed figure in a plane that is made up of SEGMENTS that intersect only at their endpoints. |
| triangle | a three-sided polygon |
| interior angle | angle formed by two adjacent sides inside of a polygon |
| scalene | a triangle with no sides congruent |
| isosceles | a triangle with at least two sides congruent |
| equilateral | a triangle with all three sides congruent |
| obtuse triangle | a triangle with an obtuse angle |
| right triangle | a triangle with a right angle |
| acute triangle | a triangle with all three angles acute |
| equiangular triangle | a triangle with all three angles congruent |
| remote interior angle | the nonadjacent (to an exterior angle) angles of the polygon. |
| opposite angle | the angle opposite a side of a triangle |
| side adjacent to an angle | one of the sides that form an angle |
| angle adjacent to a side | one of the angles formed by a side |
| opposite side | the side opposite of an angle of a triangle |
| exterior angle | angle formed by two adjacent sides outside of a polygon |
| sides | the segments which together form a polygon |
| vertices | the endpoints of the sides of a polyon |
| median | a segment from a vertex to the midpoint of the opposite side of a triangle |
| altitude | a segment from a vertex to the line containing the opposite side, perpendicular to the opposite side |
| perpendicular bisector | a segment through the midpoint of a side and perpendicular to the side |
| angle bisector | a segment from a vertex to the opposite side which bisects the angle |
| leg | one of at least two congruent sides of an isosceles triangle |
| base | the side of a triangle that is not congruent |
| vertex angle | angle opposite the base |
| base angle | angle adjacent to a base |
| convex polygon | a polygon such that no line containing a side of the polygon contains a point in its interior |
| concave polygon | a polygon that is not convex |
| regular polygon | polygon with all sides congruent and all angles congruent |
| triangle | 3-sided polygon |
| quadrilateral | 4-sided polygon |
| pentagon | 5-sided polygon |
| hexagon | 6-sided polygon |
| heptagon | 7-sided polygon |
| octagon | 8-sided polygon |
| nonagon | 9-sided polygon |
| decagon | 10-sided polygon |
| dodecagon | 12-sided polygon |
| n-gon | n-sided polygon |
| irregular polygon | polygon with at least one pair of sides or angles not congruent |
| diagonal | a segment connecting two non-adjacent vertices of a polygon |
| congruent figures | two figures that have the same size and shape |
| part | an angle or side of a triangle or polygon |
| included angle | the angle of a triangle which is adjacent to two sides of the triangle |
| included side | the side of a triangle which is adjacent to two angles of the triangle |
| non-included part | part that is not included |
| corresponding parts | parts (angles and sides) of a pair of congruent triangles (or other polygons) that are congruent |
| CPCTC | Corresponding Parts of Congruent Triangles are Congruent. |
| reflexive side | a side that is shared by two triangles. |
| SSS | a method for proving two triangles are congruent by showing all three pairs of sides are congruent |
| SAS | a method for proving two triangles are congruent by showing two pairs of sides and the included angle are congruent |
| ASA | a method for proving two triangles are congruent by showing two pairs of angles and the included side are congruent |
| AAS | a method for proving two triangles are congruent by showing two pairs of angles and the non-included side are congruent |
| HL | a method for proving two RIGHT triangles are congruent by showing the hypotenuses and one pair of legs are congruent |
| hypotenuse | the side opposite of the right angle of a right triangle. |
| leg | a side opposite an acute angle of a right triangle |
