Question: Sanjay is making a kite.
The diagram shows a sketch of his kite.
Calculate the area of the material required to make the kite.
The triangular area ABC is to be made a national park.
The bearing of B from A is 324°.
The bearing of C from A is 42°.
Calculate the area of the park.
21.5 km
14.2 km
1. **Problem 1: Area of the kite**
We are given a kite-shaped quadrilateral with diagonals measuring $25$ cm and $40$ cm, and a vertical height of $60$ cm (likely the length of one diagonal). The area of a kite can be calculated using the formula:
$$\text{Area} = \frac{1}{2} \times d_1 \times d_2$$
where $d_1$ and $d_2$ are the lengths of the diagonals.
2. **Calculate the area of the kite:**
$$\text{Area} = \frac{1}{2} \times 25 \times 40$$
$$= \frac{1}{2} \times 1000$$
$$= 500 \text{ cm}^2$$
So, the area of the kite is $500$ square centimeters.
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3. **Problem 2: Area of triangle ABC (national park)**
Given:
- Side $AB = 21.5$ km
- Side $AC = 14.2$ km
- Bearing of $B$ from $A$ is $324^\circ$
- Bearing of $C$ from $A$ is $42^\circ$
4. **Find the angle $BAC$ between sides $AB$ and $AC$:**
The angle between the two bearings is:
$$\theta = 42^\circ - 324^\circ + 360^\circ = 78^\circ$$
(We add $360^\circ$ to get a positive angle difference.)
5. **Use the formula for the area of a triangle given two sides and the included angle:**
$$\text{Area} = \frac{1}{2} \times AB \times AC \times \sin(\theta)$$
6. **Calculate the area:**
$$\text{Area} = \frac{1}{2} \times 21.5 \times 14.2 \times \sin(78^\circ)$$
Calculate $\sin(78^\circ) \approx 0.9781$:
$$\text{Area} = \frac{1}{2} \times 21.5 \times 14.2 \times 0.9781$$
$$= 0.5 \times 21.5 \times 14.2 \times 0.9781$$
$$= 149.2 \text{ km}^2$$
**Final answers:**
- Area of the kite: $500$ cm$^2$
- Area of the national park (triangle ABC): approximately $149.2$ km$^2$