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Heights, & Bisse, , OO ——, , Angle of, , Elevation —*, S|, m, , ingle formed by the line of sight with c |, the horizontal when the point is above 3 I, , } the horizontal. s, , i Height of tower 2 A B, , ] BC = ABx tan@, , |, |, Gen Abie) 0 = Angle of elevation, , ee, , V—_— ce ce ee ee ee ee ee ee — <= r The angle of elevation of a cloud from a point 60m, | The angle of elevation of the top of a tower, as seen from two points, , respectively from the foot of the tower, are complementary,, | then show that the height of the tower is /oq, , Sol. In AAOT,, , | A &B situated in the same line and at distances 'p' and ‘q’, , h, mason Se) asst), , OA p, , In ABOT, , = tan (90 -— a) = oe = ; or cot a = a «+(ii), , Multiplying (i) and (ii) , we have, , renee oe eee > te =h=Jpq, pq pq pq, , Applications, , — oe ee eee ee, >, [', vu,, , Angle of ~, Depression, , y i, e aie \ Se |, , , , © Land surveys | Angle formed by the line of sight , Horizontal _ |, with the horizontal when the ; 2 In,, @ Buildings [ point is below the horizontal. Sor, |, © optics [ | hy |, Height of tower, e \ AB = tan a x BC B c |, @ Crystallography (given o: & BC) a = Angle of Depression j, , , , , , , , above a lake is 30° and the angle of depression of, the reflection of the cloud in the lake is 60°. Find, | ! the height of the cloud from the surface of the lake., , tan 30° ae = x= BH (i), H+120 _H+120, , , , , , , , tan 60° =, , , , , , From eq. (i) and (ii), , 3H = H+ 120, , =H = 60m, , Height of the cloud from the surface, of the lake = H + 60 = 60 + 60 = 120m, , , , , , , NCERT / X / Height & Distance