Question 927684: during a preliminary survey of a future bridge site, an engineer measures the distance across a river by laying a base line 30.0 meters in length along the shore line. one end of the base line, end A, is directly across from a tree on the opposite shore line. using a sighting instrument, the engineer finds that align from the tree to the other end of the base line, end B, would form an angle of 76 degrees with the base line. what is the distance across the river?
Answer by ankor@dixie-net.com(22740)   (Show Source):
You can put this solution on YOUR website! during a preliminary survey of a future bridge site, an engineer measures the distance across a river by laying a base line 30.0 meters in length along the shore line.
one end of the base line, end A, is directly across from a tree on the opposite shore line.
using a sighting instrument, the engineer finds that align from the tree to the other end of the base line, end B, would form an angle of 76 degrees with the base line.
what is the distance across the river?
:
This forms a right triangle where the 30' baseline is the side adjacent to the 76 degree angle and the dist from the tree to a point directly across is the side opposite (s).
Use the tangent of 76 degree
tan(76) = 
s = 30 * 4.0
s = 120 ft across the river
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