Geometry Key Vocab

argument

a claim supported by reasons
claim = hypothesis
reason = proof

angle bisector

a ray that divides an angle into 2 congruent angles.

bi-conditional

The combination of a conditional statement

conditional

A conditional statement as a “if, then” sentence

conjecture

An educated guess/conclusion based on visual patterns

construction

the drawing of lines, angles, and shapes with exact percision

contrapositive

is formed by swapping and negating both parts.

Converse

Is formed by switching the if and then parts of conditional statement

counterexample

a single specific case / drawing that proves a conditional statement is false.

deductive reasoning

The logical process of using accepted fact and proven theorems to read a conclusion

Inverse

the study of inversion, maps circle and lines to others while preserving

Negation

The exact opposite or reverse of a given mathematical statement

Proof

A logical, step - by - step argument that proves it’s true.

Perpendicular bisector

A line, ray, or segment that cuts another line into 2 equal parts.

Postulate

A basic rule or statement that is accepted as true without any proof.

Theorm

A statement or rule that is not accepted on faith, but must be proven by logical reasoning.

truth table

A math chart used in logic, displays true / false possible combinations

Truth value

the status of a geometric proposition / statement

Weighted average

A method used to find a specific point on a line segment.

Ruler postulate

every point on a line can be paired with a unique real number. This number is called the coordinate of the point.

Segment addition postulate

If points A, B, and C are on the same line with B between A and C, then AB + BC = AC.

protractor postulate

If I have angle, I can assign a real. number between 0 and 180 as it’s degree measure.

Angle addition postulate

If point D is the interior of < ABC, then m<ABD = m<ABC. If I have 2 parts of an angle I can add them together to get the whole angles.

Vertical Angles Theorem

If two angles are vertical angles, then the angles are congruent.

Congruent Supplement Theorem

If 2 angles are supplementary to congruent angles (or to the same angle), then they are congruent.

Congruent complements angle

If 2 angles are complementary to congruent angles (or the same angle), then they are congruent.

Linear Pairs Theorem

the sum of the measures of a linear pair is 180.