Grade 8 Geometry Flashcards

1
Q

pyramid

A

polygon for a base and triangular sides

pyramids are named by their polygon bases

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2
Q

prism

A

2 parallel polygons for bases and rectangular sides

prisms are named by their polygon bases

cube is a special rectangular prism made of square bases and sides

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2
Q

equilateral triangle

A

a triangle whose 3 sides are the same length and whose 3 angles are the same measure (60°)

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3
Q

cone

A

circular base and a curved surface and one vertex (point) (when the curved surface is spread out flat, it is similar to a triangle)

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3
Q

isosceles triangle

A

a triangle with 2 sides are the same length and 2 angles are the same measure

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4
Q

cylinder

A

2 parallel circular bases and a curved surface (when the curved surface is spread out flat, it is in the shape of a rectangle)

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4
Q

scalene triangle

A

a triangle with no sides are the same length and no angles are the same measure

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5
Q

surface area

A

the total area of all the sides of a 3-D shape

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5
Q

acute angle

A

an angle less than 90 degrees (90°)

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6
Q

acute triangle

A

a triangle that has angles less than 90 degrees (90°)

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6
Q

right angle

A

an angle that is exactly 90 degrees (90°)

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7
Q

right triangle

A

a triangle with an angle that is exactly 90 degrees (90°)

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8
Q

obtuse angle

A

an angle more than 90 degrees (90°)

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9
Q

obtuse triangle

A

a triangle with an angle that is more 90 degrees (90°)

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10
Q

quadrilateral

A

a figure with 4 sides

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11
Q

rectangle

A

a quadrilateral with 4 right angles and 2 pairs of parallel sides, opposite sides are the same length

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12
Q

square

A

a rectangle whose 4 sides are the same length

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13
Q

parallelogram

A

a quadrilateral with 2 pairs of parallel sides, opposite sides are the same length, two opposite angles are acute and two opposite angles are obtuse

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14
Q

rhombus

A

a parallelogram whose 4 sides are the same length

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15
Q

kite

A

a quadrilateral whose adjacent (side by side, sharing an angle) sides are the same length

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16
Q

trapezoid

A

a quadrilateral with exactly 1 pair of parallel sides

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17
Q

congruent figures

A

have the same size and shape

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18
Q

similar figures

A

have the same shape, but are different sizes

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19
Q

polygon

A

a closed figure formed by 3 or more lines

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20
Q

polygon 3 sides

A

triangle

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21
Q

polygon 4 sides

A

quadrilateral

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22
Q

polygon 5 sides

A

pentagon

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23
Q

polygon 6 sides

A

hexagon

24
Q

polygon 7 sides

A

heptagon

25
Q

polygon 8 sides

A

octagon

26
Q

polygon 9 sides

A

nonagon

27
Q

polygon 10 sides

A

decagon

28
Q

sum of 3 angles of a triangle

A

180°

29
Q

sum of 4 angles of a quadrilateral

A

360°

30
Q

rotation

A

spin around a fixed point
full turn = 360°
1/2 turn = 180°
1/4 turn = 90°
1/3 turn = 120°
1/6 turn = 60°
1/8 turn = 45°

31
Q

translation

A

slide along a straight line

32
Q

reflection

A

flip over a line

33
Q

magnification

A

increase or decrease in size

34
Q

corresponding angles

A

angles that are in the same position in congruent or similar figures

35
Q

coordinate plane

A

formed by a horizontal line (x-axis) that intersects a vertical line (y-axis)

36
Q

coordinates (x, y)

A

the numbers in an ordered pair that describe the location of a point in the coordinate plane

37
Q

origin

A

the point where the x-axis and y-axis intersect (0, 0)

38
Q

parallel

A

lines that will never intersect

39
Q

perpendicular

A

lines that intersect at exactly 90°

40
Q

transversal

A

a line that cuts across a pair of parallel lines

41
Q

alternate angles

A

angles on opposite sides of a transversal, they are always congruent

42
Q

adjacent angles

A

side by side, have a common vertex and a common ray, if they are along a straight line, they add up to 180˚

43
Q

interior angles

A

angles that are inside the parallel lines

44
Q

exterior angles

A

angles that are outside the parallel lines

45
Q

vertical angles

A

opposite one another at the intersection of two lines, they are always congruent

46
Q

supplementary angles

A

two angles that add up to 180˚

47
Q

complementary angles

A

two angles that add up to 90˚

48
Q

perimeter

A

sum of the length of the sides

49
Q

radius

A

distance from the center of a circle to its edge (r = ½ d)

50
Q

diameter

A

distance from one side of a circle, through the center, to the other side (d = 2r)

51
Q

circumference

A

perimeter of a circle
C = 2πr = πd

52
Q

area

A

the number of square units inside a polygon

53
Q

formulas for area

A

A (triangle) = ½ bh
A (rectangle) = lw
A (square) = s2
A (parallelogram) = bh
A (trapezoid) = ½ h(b1+b2)
A (circle) = πr2

54
Q

formulas for surface area

A

SA of rectangular prism = 2lw+2lh+2wh = 2(lw+lh+wh)

SA of cube = 6s^2

SA of cylinder = 2πrh+2πr^2

55
Q

volume

A

amount of space enclosed in a solid (B is area of base)

volume of a cylinder = πr2h

volume of rectangular prism = lwh

volume of prism (general) = Bh

volume of pyramid (general) = 1/3 Bh

volume of cone = 1/3 Bh

56
Q

Hypotenuse

A

the side of a right-angled triangle that is opposite the right angle

57
Q

Legs

A

the sides of a right-angled triangle adjacent to the right angle, they are shorter than the hypotenuse

58
Q

Pythagorean Theorem

A

a and b are legs, c is hypotenuse

c^2 = a^2 + b^2

59
Q

y-intercept

A

the point where a graph crosses the y-axis

60
Q

x-intercept

A

the point where a graph crosses the x-axis

61
Q

slope intercept form

A

y = mx + b

62
Q

slope

A

the steepness of a line on a graph, rise over run

63
Q

scale factor

A

the number used to enlarge or reduce similar figures

64
Q

net

A

a two-dimensional pattern that forms a three-dimensional solid when formed