PSLE OQRST is part of a circle of radius 8 cm. OQS and ORT are quarter circles. The area of the shaded part ORS is 64 cm
2 and the perimeter of the shaded part ORS is 24 cm. For each of the following, use the calculator value of π to find:
- the area of the figure OQRST, correct to 1 decimal place,
- the perimeter of the figure OQRST, correct to 1 decimal place.
(a)
Area of the quarter circle
=
14 x π x 8 x 8
= 16π cm
2 Area of sector OST
= 16π - 64
Area of figure OQRST
= 16π + 16π - 64
= 32π - 64
≈ 36.5 cm
2 (Correct to 1 decimal place)
(b)
Length of arc RS
= 24 - 8 - 8
= 8 cm
Length of the arc of the quarter circle
=
14 x 2 x π x 8
= 4π cm
Length of arc ST
= (4π - 8) cm
Perimeter of the figure OQRST
= 4π + 4π - 8 + 8 + 8
= 8π + 8
≈ 33.1 cm (Correct to 1 decimal place)
Answer(s): (a) 36.5 cm
2; (b) 33.1 cm