1. **State the problem:** We have a triangle with angles 45°, 60°, and 75° (since the sum of angles in a triangle is 180°). The side opposite the 45° angle is given as $18\sqrt{2}$. We need to find the lengths $a$, $b$, and $c$ corresponding to the sides opposite the 45°, 60°, and 75° angles respectively.
2. **Use the Law of Sines:** The Law of Sines states that for any triangle,
$$\frac{a}{\sin A} = \frac{b}{\sin B} = \frac{c}{\sin C}$$
where $a$, $b$, and $c$ are sides opposite angles $A$, $B$, and $C$ respectively.
3. **Assign sides and angles:**
- Side opposite 45° is $a = 18\sqrt{2}$
- Side opposite 60° is $b$
- Side opposite 75° is $c$
4. **Calculate $b$ using Law of Sines:**
$$\frac{a}{\sin 45^\circ} = \frac{b}{\sin 60^\circ}$$
$$b = a \times \frac{\sin 60^\circ}{\sin 45^\circ}$$
Substitute $a = 18\sqrt{2}$:
$$b = 18\sqrt{2} \times \frac{\sin 60^\circ}{\sin 45^\circ}$$
Recall $\sin 45^\circ = \frac{\sqrt{2}}{2}$ and $\sin 60^\circ = \frac{\sqrt{3}}{2}$:
$$b = 18\sqrt{2} \times \frac{\frac{\sqrt{3}}{2}}{\frac{\sqrt{2}}{2}} = 18\sqrt{2} \times \frac{\sqrt{3}}{\sqrt{2}}$$
Simplify:
$$b = 18 \times \cancel{\sqrt{2}} \times \frac{\sqrt{3}}{\cancel{\sqrt{2}}} = 18\sqrt{3}$$
5. **Calculate $c$ using Law of Sines:**
$$\frac{a}{\sin 45^\circ} = \frac{c}{\sin 75^\circ}$$
$$c = a \times \frac{\sin 75^\circ}{\sin 45^\circ}$$
Substitute $a = 18\sqrt{2}$:
$$c = 18\sqrt{2} \times \frac{\sin 75^\circ}{\sin 45^\circ}$$
Recall $\sin 75^\circ = \sin(45^\circ + 30^\circ) = \sin 45^\circ \cos 30^\circ + \cos 45^\circ \sin 30^\circ = \frac{\sqrt{2}}{2} \times \frac{\sqrt{3}}{2} + \frac{\sqrt{2}}{2} \times \frac{1}{2} = \frac{\sqrt{6}}{4} + \frac{\sqrt{2}}{4} = \frac{\sqrt{6} + \sqrt{2}}{4}$:
$$c = 18\sqrt{2} \times \frac{\frac{\sqrt{6} + \sqrt{2}}{4}}{\frac{\sqrt{2}}{2}} = 18\sqrt{2} \times \frac{\sqrt{6} + \sqrt{2}}{4} \times \frac{2}{\sqrt{2}}$$
Simplify:
$$c = 18\sqrt{2} \times \frac{2}{4} \times \frac{\sqrt{6} + \sqrt{2}}{\sqrt{2}} = 18\sqrt{2} \times \frac{1}{2} \times \frac{\sqrt{6} + \sqrt{2}}{\sqrt{2}}$$
$$c = 9\sqrt{2} \times \frac{\sqrt{6} + \sqrt{2}}{\sqrt{2}} = 9 \times \cancel{\sqrt{2}} \times \frac{\sqrt{6} + \sqrt{2}}{\cancel{\sqrt{2}}} = 9(\sqrt{6} + \sqrt{2})$$
**Final answers:**
$$a = 18\sqrt{2}$$
$$b = 18\sqrt{3}$$
$$c = 9(\sqrt{6} + \sqrt{2})$$
Special Triangles 6915F2
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