1 câu trả lời
Đáp án:
\(\left[ \begin{array}{l}x=\frac{k\pi}{3}\\x=\frac{\pi}{2}+k\pi\end{array} \right.\)
(k∈Z)
Giải thích các bước giải:
sinx + 2sin3x = -sin5x
<-> 2sin3x.cos2x+2sin3x=0
<-> 2sin3x(cos2x+1)=0
<-> \(\left[ \begin{array}{l}sin3x=0\\cos2x=-1\end{array} \right.\) <-> \(\left[ \begin{array}{l}3x=k\pi\\2x=\pi +k2\pi\end{array} \right.\) <-> \(\left[ \begin{array}{l}x=\frac{k\pi}{3}\\x=\frac{\pi}{2}+k\pi\end{array} \right.\)
(k∈Z)
