A

acute angle (Lesson 1.3)

acute triangle (Lesson 1.5)

adjacent angles (Lesson 1.3)

adjacent interior angle (Lesson 4.3)

adjacent side (of an angle in a polygon) (Lesson 12.1)

alternate exterior angles See transversal. (Lesson 2.6)

alternate interior See transversal. (Lesson 2.6)

altitude See cone, cylinder, parallelogram, prism, pyramid. (Lessons 3.3, 8.1,10.1)

angle (Lesson 1.2)

angle (of a polygon) (Lesson 1.4)

angle bisector (Lessons 1.2, 3.4)

angle of depression (of an object lower than the viewer) (Lesson 12.2)

angle of elevation (of an object higher than a viewer) (Lesson 12.2)

angle of rotation(Lesson 7.1)

angular (Lesson 6.7)

annulus (Lesson 8.6)

antecedent (Chapter 12, Exploration: Three Types of Proof)

antiprism (Lesson 10.1)

apothem (of a regular polygon) (Lesson 8.4)

arc (of a circle) (Lessons 1.6, 6.3)

arc measure. See central angle. (Lesson 1.6)

Archimedean tiling See semiregular tessellation. (Lesson 7.4)

area (of a plane figure) (Lesson 8.1)

assume (Lesson 1.5)

auxiliary line (Lesson 4.1)

axis (of a cylinder) Lesson 10.1)

B

base See cone, cylinder, isosceles triangle, parallelogram, prism,

pyramid, trapezoid. (Lessons 1.5, 5.3, 10.1)

base angles (of an isosceles triangle) (Lessons 1.5, 4.2)

base angles (of a trapezoid) (Lesson 5.3)

bearing (of a direction of travel) (Lesson 6.1)

biconditional statement (Lesson 4.8)

bilateral symmetry (Lesson 0.1)

bisect Lesson 1.1; angle: Lesson 1.2)

C

center (of a circle or sphere) (circle: Lessons 1.6, 6.1, 6.4; sphere: Lesson

10.1)

center of gravity (Lesson 3.8)

central angle (of a chord or arc) (Lessons 1.6, 6.3)

centroid. (Lesson 3.8)

chord (Lessons 1.6, 6.1)

circle (Lesson 1.6)

circumcenter (Lesson 3.7)

circumference (Lesson 6.5)

circumscribed (Lesson 3.7)

classify (Lesson 1.3)

clinometer (Chapter 12,Exploration: Indirect Measurement)

coincide (Lesson 3.2)

collinear (Lesson 1.1)

compass (Lesson 0.2)

complementary angles (Lesson 1.3)

composition (of transformations) (Lesson 7.3)

concave polygon (Lesson 1.4)

concentric (circles) (Lesson 1.6)

concurrent (Lesson 3.7)

conditional proof (Chapter 12, Exploration: Three Types of Proof)

conditional statement (Chapter 10, Exploration: Sherlock Holmes and

Forms of Valid Reasoning)

cone (Lessons 1.8, 8.7, 10.3)

congruent (line segments: Lesson 1.1;angles: Lesson 1.2; polygons:

Lesson 1.4)

conjecture (Lesson 2.1)

consecutive angles (of a polygon) (Lesson 1.4)

consecutive sides (of a polygon) (Lesson 1.4)

consecutive vertices (of a polygon or polyhedron) (Lesson 1.4)

consequent (Chapter 12, Exploration: Three Types of Proof)

contrapositive (of a conditional statement) (Chapter 11, Exploration: Two

More Forms of Valid Reasoning)

converse (of a conditional statement) (Lesson 2.5)

convex polygon (Lesson 1.4)

coordinate proof (Chapter 13, Using Your Algebra Skills 10)

coplanar (Lesson 1.1)

corresponding angles See transversal. (Lesson 2.6)

cosine (of an acute angle) (Lesson 12.1)

counterexample (Lesson 1.3)

cube See hexahedron. (Lesson 10.1)

cycle (of a periodic curve) (Chapter 6, Exploration: Cycloids)

cyclic quadrilateral (Lesson 6.3)

cycloid (Chapter 6, Exploration: Cycloids)

cylinder (Lessons 1.8, 10.1)

D

data (Lesson 2.1)

decagon. (Lesson 1.4)

deductive reasoning (Lesson 2.2)

deductive system (Lesson 13.1)

definition (Lesson 1.1)

degree (Lesson 1.2)

density (Lesson 10.5)

determine (Lesson 3.6)

diagonal (Lesson 1.4)

diameter (of a circle) (Lesson 1.6)

differentiate (Lesson 1.3)

dilation (Lesson 11.1)

direct proof See indirect proof. (Chapter 12, Exploration: Three Types of

Proof)

displacement (Lesson 10.5)

dissection (Lesson 9.1)

distance (between two points) (Lesson 9.5)

distance (from a line or plane to a point) (Lesson 3.3)

distance (of a translation) (Lesson 7.1)

dodecagon (Lesson 1.4)

dodecahedron (Lesson 10.1)

dual (of a tessellation) (Lesson 7.4)

E

edge (Lesson 10.1)

elliptic geometry (Chapter 13, Exploration: Non-Euclidean Geometries)

endpoints (line segment: Lesson 1.1; arc: Lesson 1.6)

epicycloid (Chapter 6,Exploration: Cycloids)

equiangular polygon (Lesson 1.4)

equilateral polygon (polygon: Lesson 1.4; triangle: Lesson 1.5)

Euler line (Chapter 3, Exploration: The Euler Line)

Euler segment (Chapter 3, Exploration: The Euler Line)

exterior angle (of a polygon) (Lesson 5.2)

externally tangent (circles) (Lesson 6.2)

F

face (of a polyhedron) (Lesson 10.1)

flowchart (Lesson 4.7)

flowchart proof (Lesson 4.7)

fractal (Chapter 2,Exploration: Patterns in Fractals)

frustum (Lesson 8.7)

function rule (Lesson 2.3)

G

geometric mean (Lesson 13.7)

glide reflection (Lesson 7.3)

glide-reflectional symmetry (Lesson 7.3)

golden ratio (Lessons 11.3, 11.5)

golden rectangle (Lesson 11.6)

golden spiral (Lesson 11.6)

great circle (Lesson 10.1)

H

height (of a triangle, rectangle, parallelogram, trapezoid, cone, cylinder,

prism, or pyramid) (triangle: Lesson 3.3;rectangle, parallelogram: Lesson

8.1; trapezoid: Lesson 8.2; solids: Lesson 10.1)

hemisphere (Lessons 1.8, 10.1)

heptagon (Lesson 1.4)

hexagon (Lesson 1.4)

hexahedron (Lesson 10.1)

horizon line (Chapter 3,Exploration: Perspective Drawing)

hyperbolic geometry (Chapter 13, Exploration: Non-Euclidean Geometries)

hypotenuse (Lesson 9.1)

I

icosahedron (Chapter 10, Exploration: The Five Platonic Solids)

if-then statement See conditional statement.(Chapter 10, Exploration:

Sherlock Holmes and Forms of Valid Reasoning)

image (Lesson 7.1)

incenter (Lesson 3.7)

included angle (Lesson 4.4)

included side (Lesson 4.4)

incoming angle See outgoing angle.(Lesson 1.2)

indirect measurement (Lessons 11.3, 12.1)

indirect proof (Chapter 12, Exploration: Three Types of Proofs)

inductive reasoning (Lesson 2.1)

inscribed (in a circle, a semicircle, or a sphere) (Lesson 6.3)

inscribed (in a polygon or polyhedron) (Lesson 3.7)

inscribed angle (Lesson 6.1)

internally tangent (circles) See tangent circles. (Lesson 6.2)

invalid reasoning (Lesson 2.2; Chapter 10, Exploration: Sherlock Holmes

and Forms of Valid Reasoning; Chapter 11, Exploration: Two More Forms of

Valid Reasoning)

inverse (of a conditional statement) (Chapter 11, Exploration: Two More

Forms of Valid Reasoning)

inverse sine, cosine, or tangent (of a number) (Lesson 12.1)

isometric drawing (Lesson 1.8; Chapter 10, Exploration: Orthographic

Drawing)

isometry (Lesson 7.1)

isosceles trapezoid (Lesson 5.3)

isosceles (Lessons 1.5, 4.2)

K

kite.(Lessons 1.5, 5.3)

lateral edge (Lesson 10.1)

L

lateral face (of a prism or pyramid) (Lesson 10.1)

Law of Contrapositive (Chapter 11, Exploration: Two More Forms of Valid

Reasoning)

Law of Cosines (Lesson 12.4)

Law of Sines (Lesson 12.3)

Law of Syllogism (Chapter 11, Exploration: Two More Forms of Valid

Reasoning)

legs (of an isosceles triangle) (Lesson 4.2)

legs (of a right triangle) (Lesson 9.1)

lemma (Lesson 13.4)

length of an arc (Lesson 6.7)

line (Lesson 1.1)

line of best fit (Lesson 2.3)

line of reflection (Lesson 7.1)

line segment (Lesson 1.1)

line of symmetry. (Lessons 0.1, 7.1)

linear function (Lesson 2.3)

linear pair of angles (Lesson 1.3)

locus (Lesson 1.7)

logical argument (Chapter 10, Exploration: Sherlock Holmes and Forms of

Valid Reasoning)

M

major arc (Lesson 1.6)

mandala (Chapter 0 Review, Lesson 11.2)

mathematical model (Lesson 2.4)

mean (Chapter 7, Using Your Algebra Skills 7)

measure (of an angle) (Lesson 1.2)

median (of a triangle) (Lesson 3.2)

midpoint (of a line segment) (Lessons 1.1, 3.2)

midsegment (of a trapezoid) (Lesson 5.4)

midsegment (of a triangle) (Lessons 3.2, 5.4)

minimal path (Lesson 7.2)

minor arc (Lesson 1.6)

Modus Ponens (Chapter 10, Exploration: Sherlock Holmes and Forms of

Valid Reasoning)

Modus Tollens (Chapter 10, Exploration: Sherlock Holmes and Forms of

Valid Reasoning)

monohedral tiling (Lesson 7.4)

N

negation (of a statement) (Chapter 10, Exploration: Sherlock Holmes and

Forms of Valid Reasoning)

net (Lesson 1.7)

network (Chapter 2, Exploration: The Seven Bridges of Konigsberg)

n-gon (Lesson 5.1)

nonagon (Lesson 1.4)

nonrigid transformation (Lesson 7.1)

nonvertex angles (of a kite) (Lesson 5.3)

nth term (Lesson 2.3)

numerical name See vertex arrangement. (Lesson 7.4)

O

oblique See cone, cylinder, prism, and pyramid. (Lessons 1.8, 10.1)

obtuse angle (Lesson 1.3)

obtuse triangle (Lesson 1.5)

octagon (Lesson 1.4)

octahedron (Chapter 10, Exploration: Euler’s Formula for Solids)

opposite angle (of a side of a triangle) (Lesson 12.1)

opposite side (of an angle of a triangle) (Lesson 12.1)

ordered pair rule (Lesson 7.2)

orthocenter (Lesson 3.7)

orthographic drawing (Chapter 10, Exploration: Orthographic Drawing)

outgoing angle See incoming angle. (Lesson 1.2)

overlapping angles property.(Lesson 2.3)

overlapping segments property (Lesson 2.2)

P

paragraph proof (Lesson 2.5)

parallel (lines, rays, or line segments) (Lessons 1.3, 3.5)

parallel (planes or figures) (Lesson 10.1)

parallelogram (Lesson 1.5)

pentagon (Lesson 1.4)

period (Chapter 6, Exploration: Cycloids; Chapter 12, Exploration:

Trigonometric Ratios and the Unit Circle)

periodic curve (Chapter 6, Exploration: Cycloids; Chapter 12, Exploration:

Trigonometric Ratios and the Unit Circle)

perpendicular (Lesson 1.3)

perpendicular bisector (of a line segment) (Lesson 3.2)

perspective (Lesson 3.6)

plane (Lesson 1.1)

Platonic solids (Chapter 10, Exploration: The Five Platonic Solids)

point (Lesson 1.1)

point of concurrency (Lesson 3.7)

point symmetry (Lesson 7.1)

point of tangency (of a circle) (Lesson 1.6)

polygon (Lesson 1.4)

polyhedron (Lesson 10.1)

postulates (Lesson 13.1)

premises (in a deductive system) (Lesson 13.1)

prism (Lessons 1.8, 10.1)

probability (of an event) (Chapter 1, Exploration: Geometric Probability I)

proportion (Lesson 11.1)

protractor (Lesson 1.2)

pyramid (Lessons 1.8, 10.1)

Pythagorean Theorem (Lesson 9.1)

Pythagorean triple (Lesson 9.2)

Q

quadrilateral (Lesson 1.4)

R

radius (Lessons 1.6, 10.1)

ratio (Chapter 11, Using Your Algebra Skills 9)

ray (Lesson 1.1)

rectangle (Lessons 1.5, 5.6)

rectify (Lesson 8.6)

recursion (Chapter 2, Exploration: Patterns in Fractals)

recursive rule (Chapter 2, Exploration: Patterns in Fractals)

reflection (Lesson 7.1)

reflectional symmetry (Lessons 0.1, 7.1)

reflexive property of congruence (Lesson 13.1)

regular hexagon (Lesson 0.3)

regular polygon (Lesson 1.4)

regular polyhedron (Lesson 10.1)

regular tessellation (Lesson 7.4)

remote interior angles (of the exterior angle of a triangle) (Lesson 4.3)

resultant vector (Lesson 5.5)

rhombus. (Lesson 1.5)

right angle (Lesson 1.3)

right cone See cone. (Lesson 10.1)

right cylinder See cylinder. (Lesson 10.1)

right prism See prism. (Lesson 10.1)

right triangle (Lesson 1.5)

rigid transformation See isometry. (Lesson 7.1)

rotation (Lesson 7.1)

rotational symmetry (Lessons 0.1, 7.1)

S

scale factor (Lesson 11.1)

scalene triangle (Lesson 1.5)

secant (Lesson 6.3)

section (of a solid) (Lesson 1.8)

sector (of a circle) (Lesson 8.6)

segment See line segment. (Lesson 1.1)

segment (of a circle) (Lesson 8.6)

segment bisector (Lesson 3.2)

self-similar (Chapter 2, Exploration: Patterns in Fractals)

semicircle (Lesson 1.6)

semiregular tessellation (Lesson 7.4)

side (of a polygon) (Lesson 1.4)

sides (of an angle) (Lesson 1.2)

Sierpi´nski triangle (Chapter 2,Exploration: Patterns in Fractals)

similar figures (Lesson 11.1)

similar polygons (Lesson 11.1)

sine (of an acute angle) (Lesson 12.1)

skew lines (Lesson 1.8)

slant height (Lesson 8.7)

slope of a line (or line segment) (Chapter 2, Using Your Algebra Skills 2)

slope triangle (Chapter 2, Using Your Algebra Skills 2)

solid (Lesson 1.8)

solid of revolution (Lesson 1.8)

space (Lesson 1.8)

sphere (Lessons 1.8, 10.1)

square (Lessons 1.5, 5.6)

straightedge (Lesson 0.2)

supplementary angles (Lesson 1.3)

surface area (of a solid) (Lesson 8.7)

symmetric property of congruence (Lesson 13.1)

symmetry (Lesson 0.1)

T

tangent (of an acute angle).(Lesson 12.1)

tangent circles (Lesson 6.2)

tangent line (Lesson 1.6)

tangent segment (Lesson 6.2)

tangential velocity (of an object moving in a circle) (Lesson 6.7)

tessellation (Lessons 0.6, 7.4)

tetrahedron (Lesson 10.1)

theorem (Lessons 9.1, 13.1)

tile, tiling See tessellation. (Lessons 0.6, 7.4)

transformation (of a plane) (Lessons 7.1, 11.1)

transitive property of congruence (Lesson 13.1)

translation (Lesson 7.1)

translation vector See translation (Lesson 7.1)

transversal See alternate exterior angles and alternate interior angles.

(Lesson 2.6)

trapezoid. (Lessons 1.5, 5.3)

tree diagram (Lesson 1.7)

triangle (Lesson 1.5)

triangular numbers (Lesson 2.4)

trigonometry (Lesson 12.1)

truncate (Lesson 13.2)

truncated pyramid (Lesson 13.2)

two-column proof (Chapter 12, Exploration: Three Types of Proofs)

two-point perspective (Chapter 3,Exploration: Perspective Drawing)

U

undecagon (Lesson 1.4)

undefined term (Lessons 1.1, 13.1)

unit circle (Chapter 12,Exploration: Trigonometric Ratios and the Unit

Circle)

V

valid reasoning (Lesson 2.2; Chapter 10, Exploration: Sherlock Holmes and

Forms of Valid Reasoning; Chapter 11, Exploration: Two More Forms of

Valid Reasoning)

vanishing point (Chapter 3, Exploration: Perspective Drawing)

vector (Lesson 5.5)

vector sum See resultant vector. (Lesson 5.5)

Venn diagram (Lesson 1.7)

vertex See angle, polygon, and polyhedron. (Lessons 1.1, 1.4, 10.1)

vertex angle (of an isosceles triangle) (Lesson 1.5)

vertex angles (of a kite) (Lesson 5.3)

vertex arrangement (Lesson 7.4)

vertical angles (Lesson 1.3)

volume (Lesson 10.2)

W

work (Lesson 9.4)

widget (Lesson 1-3)

Y

y-intercept (Chapter 4, Using Your Algebra Skills 4)