Phương trình sinx=−12\sin x = - \frac{1}{2}sinx=−21 có tập nghiệm là
S={π6+k2π;5π6+k2π,k∈Z}S = \left\{ {\frac{\pi }{6} + k2\pi ;\frac{{5\pi }}{6} + k2\pi ,k \in \mathbb{Z}} \right\}S={6π+k2π;65π+k2π,k∈Z}
S={−π6+k2π;π6+k2π,k∈Z}S = \left\{ { - \frac{\pi }{6} + k2\pi ;\frac{\pi }{6} + k2\pi ,k \in \mathbb{Z}} \right\}S={−6π+k2π;6π+k2π,k∈Z} s
S={−π6+k2π;7π6+k2π,k∈Z}S = \left\{ { - \frac{\pi }{6} + k2\pi ;\frac{{7\pi }}{6} + k2\pi ,k \in \mathbb{Z}} \right\}S={−6π+k2π;67π+k2π,k∈Z}
S={16+k2π,k∈Z}S = \left\{ {\frac{1}{6} + k2\pi ,k \in \mathbb{Z}} \right\}S={61+k2π,k∈Z}
sinx=−12⇔[x=−π6+k2πx=π−(−π6)+k2π=7π6+k2π\sin x = - \frac{1}{2} \Leftrightarrow \left[ x=−π6+k2πx=π−(−π6)+k2π=7π6+k2π\begin{array}{l}x = - \frac{\pi }{6} + k2\pi \\x = \pi - \left( { - \frac{\pi }{6}} \right) + k2\pi = \frac{{7\pi }}{6} + k2\pi \end{array}x=−6π+k2πx=π−(−6π)+k2π=67π+k2π \right.sinx=−21⇔[x=−6π+k2πx=π−(−6π)+k2π=67π+k2π (k∈Z)\left( {k \in \mathbb{Z}} \right)(k∈Z).
