Correct option is 2) √ab
The angle of elevation of the top of a tower from two points on the ground at distances a metres and b metres from the base of the tower and in the same straight line are complementary.Prove that height of the tower is` sqrt(ab)`.
Ram Gopal Raj Shan
Asked: 3 years ago2022-10-29T00:57:58+05:30
2022-10-29T00:57:58+05:30In: Ntse
The angle of elevation of the top of a tower from two points distant a and b (a > b) from its foot and in the same straight line from it are 30° and 60°. The height of the tower is
1) a + b
2) √ab
3) √(a+b)
4) ab
The angle of elevation of the top of a tower from two points distant a and b (a > b) from its foot and in the same straight line from it are 30° and 60°. The height of the tower is
1) a + b
2) √ab
3) √(a+b)
4) ab
Leave an answer
Let height of tower is h.
Let angle at distance a is `alpha`. Then, from distance b, it will be `90-alpha`.
Then,
`tanalpha = h/a` (eq 1)
`tan(90-alpha) = h/b “cotalpha = h/b`
`tanalpha = b/h` (eq 2)
From equations1 and 2,
`h/a = b/h`
`h^2 = ab`
`h=sqrt(ab)`