-
A pilot in an aeroplane at an altitude of 200 metre observes two points lying on either side of a river. If the angles of depression of the two points be 45° and 60°, then the width of the river is
-
-
= 
200 + 200 
metre √3 -
= 200 - 200 metre √3 - 400 √3 metre
-
= 400 metre √3
-
Correct Option: A
P = Position of pilot ;
PC = 200 metre
AB = width of river
AC = x metre (let)
CB = y metre (let)
∠PAC = 45° ; ∠PBC = 60°
In ∆ APC,
| tan45° = | AC |
| ⇒ 1 = | x |
⇒ x = 200 metre
In ∆ PCB,
| tan 60° = | CB |
| ⇒ √3 = | y |
| ⇒ y = | metre | √3 |
∴ Width of river = x + y
| = | | 200 + | 200 | | metre |
| √3 |
