2000 年

If $\cos\theta=\dfrac{1}{k}$ and $0^\circ<\theta<90^\circ$, then $\tan(\theta-270^\circ)=$

The figure shows a right triangular prism. Find its volume.

In the figure, the area of $\triangle ABC$ is

In the figure, $AEC$ and $BED$ are straight lines. If the area of $\triangle ABE=4\text{ cm}^2$ and the area of $\triangle BCE=5\text{ cm}^2$, find the area of $\triangle CDE$.