$16 \sin 20^\circ \sin 40^\circ \sin 80^\circ$ is equal to:
Step-by-Step Solution
Key Concept: Recall $\sin A \sin(60^\circ - A)\sin(60^\circ + A) = \frac{1}{4} \sin 3A$. Set $A = 20^\circ$, so $\sin 60^\circ = 4 \sin 20^\circ \sin 40^\circ \sin 80^\circ$. Then scale by 16.
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Correct Answer: (2)