Să se calculeze determinanții:

1) [tex]D_{1}=\left|[tex]\begin{array}{ll}1 & 2 \\ 3 & 4\end{array}\right|[/tex]; 2) [tex]D_{2}=\left|\begin{array}{cc}C_{4}^{1} & C_{4}^{2} \\ C_{4}^{3} & C_{4}^{4}\end{array}\right| ; \quad[/tex] 3) [tex]D_{3}=\left|\begin{array}{cc}\cos \alpha & \sin \alpha \\ -\sin \alpha & \cos \alpha\end{array}\right|, \alpha \in R[/tex].[/tex]