Solve the given problems. Sketch an appropriate figure, unless the figure is given.
The diameter $d$ of a pipe can be determined by noting the distance $x$ on the $V$ -gauge shown in Fig. $4.66 .$ Points $A$ and $B$ indicate where the pipe touches the gauge, and $x$ equals either $A V$ or $V B .$ Find a formula for $d$ in terms of $x$ and $\theta$
(FIGURE CAN'T COPY)