USING FORMULAS IN GEOMETRY
Geometry CP1 (Holt 1-5) K. Santos
Area
Area (A) is the number of nonoverlapping square units of a given size that exactly cover the figure
A = 36 square units
A = 18 square units
A = 7 square units
A = ????? 14 ????
-10
-8
-6
-4
-2
0
2
4
6
8
10
-10 -8 -6 -4 -2 0 2 4 6 8 10
Area of Rectangle
Area = product of its base and height
b
A= bh h
3 ft
5 ft
A = 3(5)
A = 15 square ft
or
A = 15
Area of a Square
Area = product of its base and height
A= bh
6 in
A = 6(6)
A = 36
Area of a Triangle
Area = one half of the product of its base and height
A= bh or A = Base perpendicular to height
h h h
b b b
If b = 4” and h = 6”
Then A = (4)(6)
A = (24)
A = 12
Example—finding a side
The area of a triangle is 24 and its height is 3 cm. Find the length of its corresponding base.
A = for a triangle
24=
48 = 3b
b = 16 cm
Perimeter
Perimeter (P) of a plane figure is the sum of the side lengths of the figure
P = 24
P= 18
P = 16
P= ?-10
-8
-6
-4
-2
0
2
4
6
8
10
-10 -8 -6 -4 -2 0 2 4 6 8 10
Perimeter Formulas
Rectangle: l
P = 2l + 2w w
Square:
P = 4s s
Triangle:
P = a + b + c
a b
c
Circle Formulas
8 ft
r = 4 ft
Area:
A =
A = 16
Circumference:
C = 2r or C =
C = 8 ft
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