The shooter in exercise 67 is assumed to be in the center of the ice. Suppose that the line from the shooter to the center of the goal makes an angle of $\theta$ with center line. For the goalie to completely block the goal, he must stand $d$ feet away from the net where $d=D(1-w / 6 \cos \theta) .$ Show that for small angles, $d \approx D(1-w / 6)$