segment $($from ankle to toe$)$ is $8$ in$.$ and

the length of the lower leg $($from ankle

to knee$)$ is $18$ in$.$

$($a$)$ Given the angles shown in

Fig. P$3\mathrm{.}46($a$),$ find the position of

the knee if the runner's toes touch

the ground at the point $x=y=0.$

$($b$)$ Now suppose that the same leg is

positioned such that the knee is

located in the second quadrant and

oriented in the knee$-$down position

$($clockwise direction$),$ as shown in

Fig. P$3\mathrm{.}46.$ If the toes are located

at $.$