# Polygons F18 ```MAT091 Basic Math Skills
Module G Supplement – Sec. 6.2 Polygon Names
Name of Polygon
Number
of Sides
Example
Other Special Characteristics
Triangle
3
The sum of the measures of the three
angles is 180&deg; in every triangle
4
[ See examples of special kinds of
quadrilaterals on the back → ]
Pentagon
5
Hexagon
6
Heptagon
7
Octagon
8
Nonagon
9
Decagon
10
Dodecagon
12
Name of Polygon
Trapezoid
Number
of Sides
4
Example
Other Special Characteristics
One pair of parallel sides
[A trapezoid is also a special kind of
Parallelogram
4
Two pairs of parallel sides
[A parallelogram is a special kind of
Rhombus
4
Two pairs of parallel sides; all 4 sides
equal
[A rhombus is also a special kind of
parallelogram]
Rectangle
4
Four right angles (90&deg;); (opposite sides
parallel)
[A rectangle is also a special kind of
Square
4
Four right angles (90&deg;); all 4 sides equal
in length
[A square is also a special kind of
and rectangle]
Lessons 6.2-6.5 – Perimeter, Circumference, Area, and Volume
Formulas to Memorize:
Perimeter of any Polygon: (Just add the lengths of all the sides)
Circumference of a Circle:
C = 2πr or C = πd
[ where r = radius, d = diameter ]
Area of a Circle:
A = πr2
Area of a Rectangle:
[ where L = length, W = width ]
A = LW
[ Also remember that a square is just a rectangle with equal sides, so L = W. ]
Area of a Parallelogram:
A = bh
[ where b = base, h = height ]
Area of a Triangle:
A = &frac12;bh or A = (bh)/2
Area of a Trapezoid:
A = &frac12;h(b+c)
[since a triangle is half of a parallelogram]
[ where b and c are lengths of two parallel sides ]
Volume of a Rectangular Solid* (box with rectangular sides):
V = LWH
Volume of a Cylinder*:
V = πr2h
[*Notice that to find the volume of a solid figure with straight sides where
the parallel base and top surfaces are exactly the same, we just multiply
the area of the base by the height of the figure.]
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