The angles of elevation of the top of a tower from two points on the g...
Let AB= height of the tower=?,
and angle of elevations be ,
angle ACB =@ and angle ADB=90-@( as both the angles are complementary angles),
in right triangle ABC tan@=AB/BC,
tan@=AB/8---(1).,
in right triangle ABD tan(90-@)=AB/18,
we know that tan (90-@)=cot@,
so, cot@=AB/18,--(2),
Cot@=1/tan@,
from( 1)&(2),
AB/8=1/AB/18,
AB/8=18/AB,
AB²=18×8,
AB=√18×8=√3×3×2×2×2×2=3×2×2=12m
The angles of elevation of the top of a tower from two points on the g...
Explanation:
Let the height of the tower be 'h' meters.
Let the angles of elevation from the two points be 'θ' and '90° - θ', respectively.
We know that tan θ = height/distance
So, tan θ = h/8 ... (1)
And, tan (90° - θ) = height/distance
So, tan (90° - θ) = h/18 ... (2)
We also know that tan (90° - θ) = cot θ
So, (2) can be written as cot θ = h/18 ... (3)
Now, using (1) and (3), we can write:
h/8 × h/18 = 1
=> h² = 8 × 18
=> h² = 144
=> h = √144
=> h = 12 meters
Therefore, the height of the tower is 12 meters. Answer: (c)
To make sure you are not studying endlessly, EduRev has designed Class 10 study material, with Structured Courses, Videos, & Test Series. Plus get personalized analysis, doubt solving and improvement plans to achieve a great score in Class 10.