Question

спростить: cos4a*sin4a*cos8a

Answer 1

$\displaystyle\bf\\Cos4\alpha \cdot Sin4\alpha \cdot Cos8\alpha=\frac{1}{2} \cdot\underbrace{2Cos4\alpha Sin4\alpha }_{Sin8\alpha } \cdot Cos8\alpha =\\\\\\=\frac{1}{2} Sin8\alpha Cos8\alpha =\frac{1}{2}\cdot \frac{1}{2}\cdot \underbrace{2Sin8\alpha Cos8\alpha}_{Sin16\alpha} =\frac{1}{4} Sin16 \alpha =0,25Sin16\alpha$