Question

An observer 1.5 m tall is 28.5 m away from a chimney (see above right sided figure). The ang
or elevation of the top of the chimney from her eyes is a such that cos2a = sin(45°- a). Wh!
is the height of the chimney?
SECTION-C
WWWLWT morter​

Answer 1

Answer: 30meters

Step-by-step explanation:

Height of observer=1.5m

Angle of elevation  = cos2a=sin(45-a)

                            = cos2a= cos { 90-(45-a)}

                              = cos2a= cos 45+a

                             = 2a=45+a

                           =   a = 45°

Distance of eye of observer from foot of chimney = 28.5m

Height of chimney =

                        tan45° =  Height of chimney / 28.5

                          1 x 28.5 = Height of chimney

           Height of chimney from observer's eyes = 28.5m

          Height of chimney from observer's foot = 28.5+1.5m

                              ANS. = 30m