Triangle Solution
1. **State the problem:** Given a triangle with side $b=8.5$ inches, side $c=18.4$ inches, and angle $A=53.213^\circ$, solve for the remaining side $a$ and angles $B$ and $C$.
2. **Relevant formula and rules:** Use the Law of Sines:
$$\frac{a}{\sin A} = \frac{b}{\sin B} = \frac{c}{\sin C}$$
Since we know $b$, $c$, and $A$, we can find angle $B$ using:
$$\sin B = \frac{b \sin A}{c}$$
Important: If $\sin B > 1$, no triangle exists. If $\sin B < 1$, there may be one or two solutions depending on the angle.
3. **Calculate $\sin B$:**
$$\sin B = \frac{8.5 \times \sin 53.213^\circ}{18.4}$$
Calculate $\sin 53.213^\circ$:
$$\sin 53.213^\circ \approx 0.799$$
So,
$$\sin B = \frac{8.5 \times 0.799}{18.4} = \frac{6.7915}{18.4} \approx 0.369$$
4. **Find angle $B$:**
$$B = \sin^{-1}(0.369) \approx 21.645^\circ$$
5. **Check for second solution:**
Since $\sin B = \sin(180^\circ - B)$, the second possible angle is:
$$B' = 180^\circ - 21.645^\circ = 158.355^\circ$$
6. **Check if second solution is valid:**
Sum of angles must be $180^\circ$:
For $B'$, sum with $A$ is:
$$53.213^\circ + 158.355^\circ = 211.568^\circ > 180^\circ$$
Not possible, so only one solution exists.
7. **Find angle $C$:**
$$C = 180^\circ - A - B = 180^\circ - 53.213^\circ - 21.645^\circ = 105.142^\circ$$
8. **Find side $a$ using Law of Sines:**
$$a = c \times \frac{\sin A}{\sin C} = 18.4 \times \frac{0.799}{\sin 105.142^\circ}$$
Calculate $\sin 105.142^\circ$:
$$\sin 105.142^\circ \approx 0.966$$
So,
$$a = 18.4 \times \frac{0.799}{0.966} \approx 18.4 \times 0.827 = 15.22$$
9. **Round answers:**
$$B \approx 21.645^\circ \to 21.645^\circ$$
$$C \approx 105.142^\circ \to 105.142^\circ$$
$$a \approx 15.2$$ inches
**Final conclusion:** There is only one possible solution for the triangle with
$$B \approx 21.645^\circ, C \approx 105.142^\circ, a \approx 15.2$$ inches.