222 Basic Engineering Mathematics
Table 25.1 Formulae for the areas of common shapes
Area of plane figures
Square
x
x
Area = x 2
Rectangle
I
b
Area = l × b
Parallelogram
h
b
Area = b × h
Triangle
h
b
Area =
1
2
× b × h
Trapezium
h
b
a
Area =
1
2
(a + b)h
Circle
r
Area = πr 2 or
πd
2
4
Circumference = 2πr
Radian measure: 2π radians = 360 degrees
Sector of circle
s
r
Area =
θ ◦
360
(πr 2 )
Table 25.1 Formulae for the areas of common shapes
Area of plane figures
Square
x
x
Area = x 2
Rectangle
I
b
Area = l × b
Parallelogram
h
b
Area = b × h
Triangle
h
b
Area =
1
2
× b × h
Trapezium
h
b
a
Area =
1
2
(a + b)h
Circle
r
Area = πr 2 or
πd
2
4
Circumference = 2πr
Radian measure: 2π radians = 360 degrees
Sector of circle
s
r
Area =
θ ◦
360
(πr 2 )