Geom Vocab

Axes

x & y axis making up a graph

Coordinates

xy values giving the location of a point

right angle symbol

∟ or similar (draw or insert as image)

parallel symbol

∥

perpendicular symbol

⟂

adjacent

next to/touching

∠ or ∟

angle symbols

factor

number/variable multiplied by

ray

line w/ beginning but no end

line

line with no beginning or end

segment

line w/ a beginning and end

point

exact location on a graph represented by a dot

transformation

a change in a figure's shape, orientation, location, or size

Rigid transformation

figure changes in orientation and/or location with NO change in size or shape

Non-rigid Transformation

figure changes in size

terms

quantities (variables and/or numbers) in an expression separated by "+" or "-"

Binomial

expression containing two terms

trinomial

expression containing three terms

polynomial

expression containing more than one term

line of symmetry

line passing through the middle of a figure dividing it into 2 identical halves

corresponding

matching/occupying the same relative position

quadrilateral

4-sided closed figure

reflection

figure flipped over an imaginary line creating a mirrored image

Line of reflection

line a figure "flips over" forming a mirrored image

symbol for therefore

∴

orientation

direction a figure is facing on a graph

dilation

non-rigid transformation in which a figure shrinks or enlarges

Center of dilation

point from which the dilation occurs (point can be in the figure, on the figure's edge, or outside)

scale factor

number multiplier used to enlarge or reduce an image

translation

figure slides to a new location with no change in size, shape, or orientation

rotation

figure rotates around a point changing location and orientation

point of rotation

point around which a figure "spins" (can be in/on/outside the figure)

location

place a point or figure is found on a graph

vertex (plural vertices)

point where 2 or more lines/segments/edges meet forming an angle(s)

transversal

line which crosses two other lines

Complementary ∠s

two angles whose sum = 90°

Supplementary ∠s (aka Linear Pair)

two angles whose sum = 180°

Adjacent ∠s

two angles w/ a common vertex & a common side but no common interior points (don't overlap)

Vertical ∠s

two non-adjacent congruent angles which share a vertex (formed by two intersecting lines, segments, or opposite rays)

Corresponding ∠s

2 ∠s on same side of transversal in matching positions

Interior Angles

∠s located between parallel lines

Alternate Interior ∠s

interior ∠s on opposite sides of transversal

Exterior Angles

∠s outside parallel lines

Alternate Exterior ∠s

exterior ∠s on opposite sides of transversal

Consecutive Interior ∠s

∠s on same side of transversal between 2 lines

Acute Δ

0° < ∠ < 90°

right Δ

∠ = 90°

obtuse Δ

90° < ∠ < 180°

straight ∠

∠ = 180°

Isosceles triangle

Δ w/ 2 sides of equal length

Equilateral triangle

Δ w/ all sides =

Theorem

result/concept proven true using known facts & operations

Triangle Inequality Theorem

sum of lengths of two sides of a triangle MUST be > length of 3rd side

Triangle Sum Theorem

sum of angles of triangle add up to 180°

Pythagorean Theorem

in a right Δ, square of hypotenuse equals sum of squares of other two sides

hypotenuse

longest side of a right triangle, opposite the right angle

radical (or "root")

inverse operation to exponent

radical symbol

"check mark" symbol of the radical

index

small number on upper left of radical indicating root to take

radicand

number/term under the radical symbol

acute Δ

Δ in which all 3 angles are less than 90°

right Δ

Δ in which one ∠ = 90°

obtuse Δ

Δ in which one ∠ is greater than 90°

base

number/variable raised to a power

exponent or power or index

small number above & right of base

≈

symbol for approximately

~

similar (same shape)

approximately

≈

similar

figures w/ same shape & proportions (of their sides)

congruent / congruence

identical or equivalent

bisector

line dividing segment or angle into two equal parts

perpendicular bisector

segment from triangle's vertex to midpoint of opposite side AND makes a right angle

Included Angle

∠ located between two sides on a figure

Included Side

side located between two ∠s on a figure

origin

point at the center of a circle

radius

line from origin to edge of circle

diameter

chord passing through origin from one edge to the other

chord

segment from one edge of a circle to the other

arc

part of a circle's circumference

minor arc

arc w/ central ∠ less than 180°

major arc

arc w/ central ∠ more than 180°

central angle

formed by two radii with vertex at origin

degree

measurement for ∠s based on a circle (full rotation = 360 units)

radian

unit for ∠s based on angle when arc length = radius

sector

portion of circle enclosed by two radii and an arc

Circumference

perimeter of a circle

θ

symbol (theta) used for unknown ∠

sine

in a right triangle, ratio of opposite side to hypotenuse

cosine

in a right triangle, ratio of adjacent side to hypotenuse

tangent function

in a right triangle, ratio of opposite to adjacent

tangent

line touching circle at only 1 point, perpendicular to radius there

cosecant

reciprocal of sine

secant

reciprocal of cosine

cotangent

reciprocal of tangent

arcsin (sin⁻¹)

inverse function of sine

arccos (cos⁻¹)

inverse function of cosine

arctan (tan⁻¹)

inverse function of tangent

adjacent side

in a triangle, side touching θ (never hypotenuse)

apex

vertex at highest point/top

polygon

closed figure with 3 or more angles