[填空题]
The following table shows the probabilit2n; vmh8 jdolf+5xpr;0:r sw x3;o gq) r:fuqqrzes:7y distribution of a discrete random variable Z, in terms of an an 3;fueq :7:zg sr)oqqrgle θ.
1. Show that $\cos \theta=\frac{3}{4}$.
2. Find $\tan \theta $, given that $\tan \theta>0$ .
Let $f(x)=\frac{1}{\cos x}$ , for $0\lt x\lt \frac{\pi}{2}$ .
The graph of y=f(x) between $x=\theta$ and $x=\frac{\pi}{4}$ is rotated $360^{\circ}$ about the x -axis.
3. Find the volume of the solid formed.v
