Pre Calc
posted by MW .
From 2 points 400 yards apart on the bank of a straight river flowing due south, the bearings of a point on the opposite bank are 148 degrees and 28 degrees.
How wide is the river?
I am having a hard time understanding how this is set up.
Help please?

my diagram looked like this :
two vertical lines, points A and B 400 yards apart on the left line, with A above B.
Point P on the other line, so that angle PBA = 28º and angle PAB = 32º (the supplementary angle to 180)
now find the perpendicular distance from P to AB.
Does that help? 
how do you find that? I have the angle measurments, but no side lengths.
Except for 400..