Sector Calculations
1. Given: OS = 7 cm and R is the midpoint of OS, so OR = RS = 3.5 cm.
2. (a) Diameter of OS: Since OS is a radius, diameter = 2 \times OS = 2 \times 7 = 14 cm.
3. (b) Perimeter of sector OSR includes two radii and arc OSR.
- Radius OR = 3.5 cm (half OS)
- Arc length of sector OSR = \frac{\theta}{360} \times 2 \pi r = \frac{40}{360} \times 2 \times \frac{22}{7} \times 3.5.
Calculate arc length:
$$\frac{40}{360} \times 2 \times \frac{22}{7} \times 3.5 = \frac{1}{9} \times 2 \times 11 = \frac{22}{9} \approx 2.44 \text{ cm}.$$
- Perimeter = OR + RS + arc length = 3.5 + 3.5 + 2.44 = 9.44 cm.
4. (c) Area of shaded region (sector OST) = total sector OS area - area of ORU:
- Area of sector OS (radius 7 cm, angle 40°):
$$\frac{40}{360} \times \pi \times 7^2 = \frac{1}{9} \times \pi \times 49 = \frac{49 \pi}{9}.$$
Using \( \pi = \frac{22}{7} \), area = \(\frac{49 \times 22}{9 \times 7} = \frac{49 \times 22}{63} = \frac{1078}{63} \approx 17.11 \text{ cm}^2.\)
- Area of unshaded region ORU (radius 3.5 cm, angle 40°) given:
$$\frac{40}{360} \times \pi \times (3.5)^2 = \frac{22}{9} \approx 2.44 \text{ cm}^2.$$
- Therefore, shaded area = area sector OS - area ORU = 17.11 - 2.44 = 14.67 cm².
5. Final answers rounded to two decimal places:
(a) Diameter = 14.00 cm
(b) Perimeter = 9.44 cm
(c) Area of shaded region = 14.67 cm²