JEE Main | 2014Trigonometric EquationHard

Question

A bird is sitting on the top of a vertical pole 20 m high and its elevation from a point O on the ground is 45o. It flies off horizontally straight away from the point O. After one second, the elevation of the bird from O is reduced to 30o. Then the speed (in m/s) of the bird is

Options

A.20√2
B.20(√3 - 1)
C.40(√2 - 1)
D.40(√3 - √2)

Solution

       
t = 1 s
From figure tan 45o =
and tan 30 o =
so, y = 20(√3 - 1)
i.e., speed = 20(√3 - 1) m/s.

Create a free account to view solution

View Solution Free
Topic: Trigonometric Equation·Practice all Trigonometric Equation questions

More Trigonometric Equation Questions

Let f(n) = tan-1 + tan-1 + tan-1 + .... n terms, then f(n) is -...If f(x) = 2tan-1x + sin-1 , x > 1, then f(5) is equal to...If 2 ≤ a < 3, then the value of cos-1 cos [a]+ cosec-1 cosec[a]+ cot-1 cot[a] , (where [.] denotes greatest int...In a triangle ABC, ∠B = and ∠C = LetDdivides BC internally in the ration 1 : 3, then is equal to...If 0 ≤ x ≤ 3π, 0 ≤ y ≤ 3π and cos x. sin y = 1 then the possible number of values of t...