Thanks supratim1, I appreciate it.
Upon further investigation I realized how simple the solution to this problem is, hah. I guess I owe it to a brain fart.
Thanks for the reply.
1. Jean camps beside a wide river and wonders how wide it is. She spots a large rock on the bank directly across from her. She then walks upstream until she judges that the angle between her and the rock, which she can still see clearly, is now at an angle of 30 downstream (as shown in the...