The length of the latus rectum of the parabola whose focus is \(\left(\frac{u^2}{2 g} \sin 2 \alpha,-\frac{u^2}{2 g} \cos 2 \alpha\right)\) and directrix is \(y=\frac{u^2}{2 g}\), is
1
\( \frac{u^2}{g} \cos ^2 \alpha\)
2
\( \frac{u^2}{g} \cos 2 \alpha\)
3
\( \frac{2 u^2}{g} \cos ^2 2 \alpha\)
4
\( \frac{2 u^2}{g} \cos ^2 \alpha \)