Question 43

Mathematics Trigonometric Equations Hard

The value of sin 20° sin 40° sin 80° is

(A) <span class="math-tex">\(\dfrac{1}{2}\)</span>
(B) <span class="math-tex">\(\dfrac{\sqrt{3}}{2}\)</span>
(C) <span class="math-tex">\(\dfrac{\sqrt{3}}{8}\)</span>
(D) <span class="math-tex">\(\dfrac{1}{8}\)</span>
✓ Correct Answer: Option C Verified Solution

📘 Step-by-Step Solution & Detailed Explanation:

\[ \sin 20^\circ \sin 40^\circ \sin 80^\circ \] We know that: \[ \sin A \sin(60^\circ - A) \sin(60^\circ + A) = \frac{1}{4} \sin 3A \] Thus, \[ \sin 20^\circ \sin 40^\circ \sin 80^\circ = \frac{1}{4} \times \sin(20^\circ \times 3) \] \[ \sin 20^\circ \sin 40^\circ \sin 80^\circ = \frac{\sqrt{3}}{8} \]

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