Practicing Success
From the top of a lamp post of height x metres, two objects on the ground on the same side of it (and in line with the foot of the lamp post) are observed at angles of depression of $30^\circ$ and $60^\circ$, respectively. The distance between the objects is $32\sqrt{3}$ m. The value of x is: |
36 48 54 45 |
48 |
⇒ In triangle PQS, ⇒ tan\({30}^\circ\) = \(\frac{x}{QS}\) ⇒ \(\frac{1}{√3}\) = \(\frac{x}{QS}\) ⇒ x = \(\frac{QS}{√3}\) ..(1.) ⇒ In triangle PQR ⇒ tan\({60}^\circ\) = \(\frac{PQ}{QR}\) ⇒ \(\sqrt { 3}\) = \(\frac{x}{QR}\) ⇒ x = QR\(\sqrt {3 }\) ..(2.) ⇒ From equation (1.) and (2.) ⇒ QR\(\sqrt {3 }\) = \(\frac{QS}{√3}\) ⇒ 3QR = QS ⇒ QS = QR + RS ⇒ 3QR = QR + RS ⇒ 2QR = RS ⇒ 2QR = 32\(\sqrt {3 }\) ⇒ QR = 16\(\sqrt {3 }\) ⇒ x = 16\(\sqrt {3 }\) x \(\sqrt {3 }\) = 48m. |