trig
posted by Anonymous .
from an observer tower, a ff.above the level of a river,the angle of depression of a point on the near shore is theta and that of a point directly beyond on the far shore is FI. show that the width of the river is a (cotan theta=p+q/r)

I cannot decipher your problem.
Where do p, q, and r come from?
what is ff and FI ?