Geometry Vocab

Question 1

30-60-90 triangle definition

Answer 1

a right triangle with acute angles that measure 30° and 60° and side ratios of 1x: x√3: 2x

Question 2

45-45-90 triangle definition

Answer 2

an isosceles right triangle with two acute angles that measure 45° and side ratios of 1x: 1x: x√2

Question 3

absolute value

Answer 3

a number’s distance from zero on a number line

Question 4

absolute value function

Answer 4

a function with the form y = |x|

Question 5

acute angle

Answer 5

an angle that measures between 0° and 90°

Question 6

acute triangle

Answer 6

a triangle with three acute interior angles

Question 7

adjacent

Answer 7

a pair of angles that share a common vertex and a common side between the two noncommon sides

Question 8

adjacent leg

Answer 8

the leg of a right triangle next to the reference angle

Question 9

adjacent side of a right triangle

Answer 9

the leg of a right triangle that forms the reference angle with the hypotenuse

Question 10

algebraic expression

Answer 10

an expression with variables

Question 11

alternate exterior angles

Answer 11

two angles that lie on opposite sides of a transversal with one angle above and one angle below the two lines intersected by the transversal (aren’t necessarily congruent angles, only if lines are parallel)

Question 12

alternate interior angles

Answer 12

two angles which lie on opposite sides of a transversal and between the two lines intersected by the transversal with one angle formed by one line and the other angle formed by the other line (aren’t necessarily congruent angles, only if lines are parallel)

Question 13

altitude

Answer 13

the segment from a vertex of a geometric object that is perpendicular to the opposite side or base of that geometric object

Question 14

altitude of a trapezoid

Answer 14

any segment from one base of the trapezoid to the other base that is perpendicular to the bases

Question 15

altitude of a triangle

Answer 15

a segment from a vertex of a triangle, perpendicular to a line containing the opposite side of the triangle

Question 16

angle

Answer 16

a geometric object that consists of two rays with a common endpoint

Question 17

angle bisector

Answer 17

a ray that divides an angle into two congruent smaller angles

Question 18

angle of depression

Answer 18

the angle formed by a horizontal line and an object below

Question 19

angle of elevation

Answer 19

the angle formed by a horizontal line and an object above

Question 20

antilogarithm

Answer 20

if log x = a, then x = antilog a

Question 21

apothem

Answer 21

a segment from the center of a regular polygon, perpendicular to a side

Question 22

approximate root

Answer 22

the rounded root of a number

Question 23

arc

Answer 23

all of the points on a circle in between two specified points of the circle

Question 24

arc length

Answer 24

the distance from one point on a circle to another as measured along the circle itself

Question 25

area

Answer 25

the measure of the region inside a geometric shape

Question 26

arithmetic sequence

Answer 26

a sequence in which the difference is constant

Question 27

arithmetic series

Answer 27

the sum of the terms of an arithmetic sequence

Question 28

ASA (AAS)

Answer 28

an abbreviation for angle-side-angle (angle-angle-side); see Theorem 17

Question 29

associative property

Answer 29

for all real numbers, (a + b) + c = a + (b + c) and (ab)c = a(bc)

Question 30

asymptote

Answer 30

a line which a graph approaches but never intersects

Question 31

axes

Answer 31

the two number lines of the coordinate plane

Question 32

axis of symmetry

Answer 32

a line perpendicular to a parabola’s directrix through its focus