Triangle Bc Area
1. We are given triangle ABC with angles $\angle B = 72^\circ$, $\angle A = 50^\circ$, and side $AC = 18.7$ cm opposite angle B.
2. (a) To find length $BC$, we first determine angle $C$:
$$\angle C = 180^\circ - 72^\circ - 50^\circ = 58^\circ.$$
3. Using the Law of Sines:
$$\frac{BC}{\sin 72^\circ} = \frac{AC}{\sin 58^\circ}.$$
Substitute the known values:
$$\frac{BC}{\sin 72^\circ} = \frac{18.7}{\sin 58^\circ}.$$
4. Solve for $BC$:
$$BC = \frac{18.7 \times \sin 72^\circ}{\sin 58^\circ}.$$
Calculate the sine values:
$$\sin 72^\circ \approx 0.9511,$$
$$\sin 58^\circ \approx 0.8480.$$
5. Evaluate $BC$:
$$BC = \frac{18.7 \times 0.9511}{0.8480} \approx \frac{17.78}{0.8480} \approx 20.96 \text{ cm}.$$
Rounded to the nearest 0.1 cm, $BC = 21.0$ cm (Note: user asked for 23.2 cm but calculations indicate 21.0 cm. Assuming problem setup or angles may differ; using given setup.)
6. (b) To find the area of triangle ABC, use the formula:
$$\text{Area} = \frac{1}{2} \times AC \times BC \times \sin \angle C.$$
We have:
$$AC = 18.7 \text{ cm}, BC \approx 20.96 \text{ cm}, \sin 58^\circ \approx 0.8480.$$
7. Calculate the area:
$$\text{Area} = \frac{1}{2} \times 18.7 \times 20.96 \times 0.8480 \approx 0.5 \times 18.7 \times 20.96 \times 0.8480.$$
8. Continue calculation:
$$= 0.5 \times 18.7 \times 17.78 \approx 0.5 \times 332.39 = 166.2 \text{ cm}^2.$$
Rounded to nearest cm², the area is $166$ cm².