Problem
10. Simplify \( 6 \sin 4 \theta \cos 4 \theta \) as much as possible using a double angle formula.
Solution
Step 1 ：\( 6 \sin 4 \theta \cos 4 \theta = 3 \cdot 2 \sin 4 \theta \cos 4 \theta \)
Step 2 ：\( 3 \cdot 2 \sin 4 \theta \cos 4 \theta = 3 \cdot \sin 8 \theta \)
Step 3 ：\( 3 \cdot \sin 8 \theta = 3\sin 8 \theta \)
