IIT JEE , AIEEE Forum - Mathematics , Trignometry

vikram1989

There is a reef at the river mouth of a river.

Alight house is built on the reef.The surfae of which is at the same height of the light house.

The only equipment available is a compass theodolite(to measure vertical and horizontal angles) and a measuring tape.

The light house cannot be reached directly from the river bank.

Indicate measurements that could be taken and derive a formula for the heght of the light housse in terms of these measurements.Cleatly state the meanoing of all symbols that you use.

The riverbank is horizontal.

pink_ele

hmmm..........
let height be h.
here take the measuring tape and measure a distance let say "d".......from d river bank fyn...........
now mesure a angles of elevation from those two points............okies
let say angeles are A amd B where B>Anow using trogonometry we have,
let say x=distanc of light house from other bank...........
thus
x=h cotB
and
x+d=h cot A
thush=d/(cotA-cotB)

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