Let a be the length of a side of square plot ABCD and h, the height of the pole standing at D. Since elevations of P from A or C is 30° and that from B is Θ,
∴ In triangle Δ PCD, tan 30° = h/a
i.e h/a = 1/√3 .............. (1)
And in triangle Δ PBD,
Since PD = h and BD = √(AB2 + AD)2 = a√2.
Put the value of PD and BD , we will get
tan Θ = PD/BD = h/(a√2)
put the value of h/a from equation (1)
tan Θ = 1/√2 x 1/√3
tan Θ = 1/√6