Grade 8 Geometry Flashcards
pyramid
polygon for a base and triangular sides
pyramids are named by their polygon bases
prism
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
equilateral triangle
a triangle whose 3 sides are the same length and whose 3 angles are the same measure (60°)
cone
circular base and a curved surface and one vertex (point) (when the curved surface is spread out flat, it is similar to a triangle)
isosceles triangle
a triangle with 2 sides are the same length and 2 angles are the same measure
cylinder
2 parallel circular bases and a curved surface (when the curved surface is spread out flat, it is in the shape of a rectangle)
scalene triangle
a triangle with no sides are the same length and no angles are the same measure
surface area
the total area of all the sides of a 3-D shape
acute angle
an angle less than 90 degrees (90°)
acute triangle
a triangle that has angles less than 90 degrees (90°)
right angle
an angle that is exactly 90 degrees (90°)
right triangle
a triangle with an angle that is exactly 90 degrees (90°)
obtuse angle
an angle more than 90 degrees (90°)
obtuse triangle
a triangle with an angle that is more 90 degrees (90°)
quadrilateral
a figure with 4 sides
rectangle
a quadrilateral with 4 right angles and 2 pairs of parallel sides, opposite sides are the same length
square
a rectangle whose 4 sides are the same length
parallelogram
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
rhombus
a parallelogram whose 4 sides are the same length
kite
a quadrilateral whose adjacent (side by side, sharing an angle) sides are the same length
trapezoid
a quadrilateral with exactly 1 pair of parallel sides
congruent figures
have the same size and shape
similar figures
have the same shape, but are different sizes
polygon
a closed figure formed by 3 or more lines
polygon 3 sides
triangle
polygon 4 sides
quadrilateral
polygon 5 sides
pentagon
polygon 6 sides
hexagon
polygon 7 sides
heptagon
polygon 8 sides
octagon
polygon 9 sides
nonagon
polygon 10 sides
decagon
sum of 3 angles of a triangle
180°
sum of 4 angles of a quadrilateral
360°
rotation
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°
translation
slide along a straight line
reflection
flip over a line
magnification
increase or decrease in size
corresponding angles
angles that are in the same position in congruent or similar figures
coordinate plane
formed by a horizontal line (x-axis) that intersects a vertical line (y-axis)
coordinates (x, y)
the numbers in an ordered pair that describe the location of a point in the coordinate plane
origin
the point where the x-axis and y-axis intersect (0, 0)
parallel
lines that will never intersect
perpendicular
lines that intersect at exactly 90°
transversal
a line that cuts across a pair of parallel lines
alternate angles
angles on opposite sides of a transversal, they are always congruent
adjacent angles
side by side, have a common vertex and a common ray, if they are along a straight line, they add up to 180˚
interior angles
angles that are inside the parallel lines
exterior angles
angles that are outside the parallel lines
vertical angles
opposite one another at the intersection of two lines, they are always congruent
supplementary angles
two angles that add up to 180˚
complementary angles
two angles that add up to 90˚
perimeter
sum of the length of the sides
radius
distance from the center of a circle to its edge (r = ½ d)
diameter
distance from one side of a circle, through the center, to the other side (d = 2r)
circumference
perimeter of a circle
C = 2πr = πd
area
the number of square units inside a polygon
formulas for area
A (triangle) = ½ bh
A (rectangle) = lw
A (square) = s2
A (parallelogram) = bh
A (trapezoid) = ½ h(b1+b2)
A (circle) = πr2
formulas for surface area
SA of rectangular prism = 2lw+2lh+2wh = 2(lw+lh+wh)
SA of cube = 6s^2
SA of cylinder = 2πrh+2πr^2
volume
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
Hypotenuse
the side of a right-angled triangle that is opposite the right angle
Legs
the sides of a right-angled triangle adjacent to the right angle, they are shorter than the hypotenuse
Pythagorean Theorem
a and b are legs, c is hypotenuse
c^2 = a^2 + b^2
y-intercept
the point where a graph crosses the y-axis
x-intercept
the point where a graph crosses the x-axis
slope intercept form
y = mx + b
slope
the steepness of a line on a graph, rise over run
scale factor
the number used to enlarge or reduce similar figures
net
a two-dimensional pattern that forms a three-dimensional solid when formed
