Sector Segment Areas
1. **Calculate the area of the sector of a circle with radius 65 mm and sector angle 42°.**
- The formula for the area of a sector is $$Area = \frac{\theta}{360} \times \pi r^2$$ where $\theta$ is the sector angle in degrees and $r$ is the radius.
- Given: $r = 65$ mm and $\theta = 42^\circ$.
- Convert radius into cm: $65$ mm = $6.5$ cm.
- Calculate the area:
$$Area = \frac{42}{360} \times \pi \times (6.5)^2 = \frac{42}{360} \times \pi \times 42.25$$
$$Area \approx 0.1167 \times 3.1416 \times 42.25 \approx 15.48\ \text{cm}^2$$
2. **Work out the area of the shaded segment formed by a quarter circle with radius 4.8 cm and chord AC.**
- The arc ABC is a quarter circle, so $\theta = 90^\circ$.
- Radius $r = 4.8$ cm.
- Calculate the area of the sector:
$$Area_{sector} = \frac{90}{360} \times \pi \times (4.8)^2 = \frac{1}{4} \times \pi \times 23.04 = 18.1\ \text{cm}^2$$
- Calculate the length of chord AC using the right triangle formed:
$$AC = \sqrt{(4.8)^2 + (4.8)^2} = \sqrt{46.08} = 6.788\ \text{cm}$$
- Calculate the area of triangle OAC:
$$Area_{triangle} = \frac{1}{2} \times 4.8 \times 4.8 = 11.52\ \text{cm}^2$$
- The shaded segment area = sector area - triangle area:
$$Area_{segment} = 18.1 - 11.52 = 6.58\ \text{cm}^2$$
- Rounded to 3 significant figures: $6.58$ cm².
**Final answers:**
1. Sector area = $15.48$ cm².
2. Segment area = $6.58$ cm².