Surveyor wishes to measure the distance across a stream. He sets up his transit at a point C on the bank of the stream, and sights on a point B on the other
bank directly opposite him. Then he turns the transit through a right angle
and measures off a distance of 100 feet to a point A. He moves the transit to
A, and measures the angle CAB, which he finds to be 50°. How wide is the
stream?