A biologist wants to know the width w of a river so that instruments for studying the pollutants in the water can be set properly. From point A, the biologist walks downstream 100 feet and sights to point C. From the sighting, it is determined that theta = 54°. How wide is the river? Round to the nearest tenth.

Answer 1

Poor wording. Where is C?
I will assume that C is on the other side of the river directly across from A
and theta is the angle the river forms with the line to C from his destination.

so AC/100 to tan 54°
AC = 100tan54 = ....