1. **State the problem:** Given a triangle with \(m\angle B = 19^\circ\), side \(a = 30\) yd opposite \(\angle A\), and side \(b = 12\) yd opposite \(\angle B\), find the remaining angle \(m\angle A\), \(m\angle C\), and side \(c\).
2. **Recall the Law of Sines:**
$$\frac{a}{\sin A} = \frac{b}{\sin B} = \frac{c}{\sin C}$$
This law relates sides and their opposite angles in any triangle.
3. **Find \(m\angle A\):**
Using the Law of Sines,
$$\frac{a}{\sin A} = \frac{b}{\sin B} \implies \frac{30}{\sin A} = \frac{12}{\sin 19^\circ}$$
Cross-multiplied:
$$30 \sin 19^\circ = 12 \sin A$$
Divide both sides by 12:
$$\frac{30}{\cancel{12}} \sin 19^\circ = \frac{12}{\cancel{12}} \sin A \implies \frac{30}{12} \sin 19^\circ = \sin A$$
Calculate:
$$\sin A = 2.5 \times \sin 19^\circ \approx 2.5 \times 0.32557 = 0.8139$$
Find \(A\):
$$m\angle A = \sin^{-1}(0.8139) \approx 54.7^\circ$$
4. **Find \(m\angle C\):**
Sum of angles in a triangle is 180°:
$$m\angle C = 180^\circ - m\angle A - m\angle B = 180^\circ - 54.7^\circ - 19^\circ = 106.3^\circ$$
5. **Find side \(c\) using Law of Sines:**
$$\frac{c}{\sin C} = \frac{a}{\sin A} \implies c = \frac{a \sin C}{\sin A} = \frac{30 \times \sin 106.3^\circ}{\sin 54.7^\circ}$$
Calculate:
$$c = \frac{30 \times 0.9703}{0.8139} \approx \frac{29.11}{0.8139} = 35.77\text{ yd}$$
**Final answers:**
$$m\angle A \approx 54.7^\circ$$
$$m\angle C \approx 106.3^\circ$$
$$c \approx 35.8\text{ yd}$$
Triangle Law Sines 2Fedb6
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