Question

A person in an helicopter flying at a height of 700 meters, observes two objects lying opposite to each other on either side of the bank of a river. The angles of depression of the objects are 35° and 50°. Find the width of the river to the nearest foot.

A. 412 ft
B 1000 ft
C 1342 ft
D 1587 ft

Answer 1

Let C be the position of a person in a helicopter. A,B be two objects lying opposite to each other on either bank of a river.

Let AD=x,BD=y

In ΔACD,

⇒tan30

o

=

AD

CD

​

⇒

3

​

1

​

=

x

700

​

⇒x=130

3

​

⇒x=130(1.732)=1212.4

∴ the width of the river =x+y

=1212.4+130

=1342.4m

Explanation: