Determina sen $\alpha$ sapendo che :
$$
\begin{aligned}
& \cos \alpha=\frac{1}{2} ; \frac{\pi}{2}<\alpha<\pi \\
& \cos \alpha=\frac{1}{3} ; \frac{3 \pi}{2}<\alpha<2 \pi
\end{aligned}
$$
Determina sen $\alpha$ sapendo che :
$$
\begin{aligned}
& \cos \alpha=\frac{1}{2} ; \frac{\pi}{2}<\alpha<\pi \\
& \cos \alpha=\frac{1}{3} ; \frac{3 \pi}{2}<\alpha<2 \pi
\end{aligned}
$$