Page 624 - Ultimate Visual Dictionary (DK)

APPENDIX
Shapes: Plane

Two-dimensional shapes are termed plane (or flat) shapes. Plane
AREAS AND
AREAS AND
AREAS AND
shapes constructed with straight sides, as illustrated here, are PERIMETERS
PERIMETERS
PERIMETERS
called polygons. They are categorized according to the number of The formulae for
sides they have—for example, three-sided polygons are known as calculating the areas and
perimeters of simple plane
triangles. A polygon that has sides of shapes were devised by
equal length and internal angles of Classical Greek
equal size, such as a square, mathematicians.
is said to be regular.
r
d

SCALENE TRIANGLE ISOSCELES TRIANGLE RIGHT-ANGLED TRIANGLE
A triangle (three-sided A triangle with only two sides A triangle with one angle
polygon) with no and two angles equal. as a right angle (90º).
equal sides or angles.
CIRCLE
r = radius
d = diameter = 2 r
Circumference = 2 π r
Area = π r 2
(π = 3.1416)

EQUILATERAL TRIANGLE SQUARE RHOMBUS
A regular triangle. A regular quadrilateral. A quadrilateral with all sides
All angles are 60º. All angles are 90º. equal and two pairs of
equal angles. a c
h

b

TRIANGLE
Height = h
Sides = a, b, c
Perimeter = a + b + c
Area = ½ b h
RECTANGLE PARALLELOGRAM TRAPEZIUM
A quadrilateral with four right A quadrilateral with two A quadrilateral with one pair
angles and opposite sides of pairs of parallel sides. of parallel sides.
equal length.

b

a

RECTANGLE
Sides = a, b
PENTAGON HEXAGON OCTAGON
A five-sided polygon. A regular A six-sided polygon. A regular An eight-sided polygon. A Perimeter = 2 (a + b)
pentagon is shown above. hexagon is shown above. regular octagon is shown above. Area = a b

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