1. **State the problem:** We have a right triangle with one side length 28 mm opposite a 60° angle, and we want to find the hypotenuse $s$. 2. **Recall the sine function:** In a right triangle, $\sin(\theta) = \frac{\text{opposite}}{\text{hypotenuse}}$. 3. **Apply the formula:** Here, $\theta = 60^\circ$, opposite side = 28 mm, hypotenuse = $s$. $$\sin(60^\circ) = \frac{28}{s}$$ 4. **Use the exact value:** $\sin(60^\circ) = \frac{\sqrt{3}}{2}$. $$\frac{\sqrt{3}}{2} = \frac{28}{s}$$ 5. **Solve for $s$:** Multiply both sides by $s$ and then divide both sides by $\frac{\sqrt{3}}{2}$: $$s = \frac{28}{\frac{\sqrt{3}}{2}}$$ 6. **Simplify the complex fraction:** $$s = 28 \times \frac{2}{\sqrt{3}}$$ 7. **Multiply:** $$s = \frac{56}{\sqrt{3}}$$ 8. **Rationalize the denominator:** Multiply numerator and denominator by $\sqrt{3}$: $$s = \frac{56}{\sqrt{3}} \times \frac{\sqrt{3}}{\sqrt{3}} = \frac{56\sqrt{3}}{3}$$ **Final answer:** $$s = \frac{56\sqrt{3}}{3} \text{ mm}$$