= 1 km × 1 km = 1 000 m × 1 000 m = 10 000 m2 = 1 m × 1 m = 100 cm × 100 cm = 10 000 cm2 = 1 cm × 1 cm = 10 mm × 10 mm = 100 mm2
Triangle x Length (l)
Perimeter = l + l + l + l = 4 (l)
Area = l × l = l2 Circle Radius (r) Radius (r) θ Radius (r)
Perimeter = 2 × π × radius = 2πr
Area = π × r 2 = π r 2
Perimeter of a circle is also known as its circumference.
Perimeter = π × r + diameter = πr + d
Area = 1 Area = 1
__ 2 × π × r 2
__ 2 π r 2
Length of arc = θ
___ 360 × 2π × r
Total perimeter = arc + 2r Area of sector = θ
___ 360 × π × r 2
Length (l)
Perimeter = l + w + l + w = 2 (l) + 2 (w)
Area = l × w Semicircle
Base (b) z
Perimeter = x + y + z Area = 1 Area = 1
__ 2 b × ⊥h
Sector Arc
_ 2 base × perpendicular height
y
Worked example 1 For the sector shown, fi nd: (i) the area, in terms of π (ii) the arc length, in terms of π (iii) the perim eter, to one decimal place.