PSLE OQRST is part of a circle of radius 13 cm. OQS and ORT are quarter circles. The area of the shaded part ORS is 78 cm
2 and the perimeter of the shaded part ORS is 52 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 13 x 13
= 42.25π cm
2 Area of sector OST
= 42.25π - 78
Area of figure OQRST
= 42.25π + 42.25π - 78
= 84.5π - 78
≈ 187.5 cm
2 (Correct to 1 decimal place)
(b)
Length of arc RS
= 52 - 13 - 13
= 26 cm
Length of the arc of the quarter circle
=
14 x 2 x π x 13
= 6.5π cm
Length of arc ST
= (6.5π - 13) cm
Perimeter of the figure OQRST
= 6.5π + 6.5π - 13 + 13 + 13
= 13π + 13
≈ 53.8 cm (Correct to 1 decimal place)
Answer(s): (a) 187.5 cm
2; (b) 53.8 cm