A tree breaks due to storm and the broken part bends, so that the top of the tree touches the ground making an angle of 30° with the ground. The distance between the foot of the tree to the point where the top touches the ground is 18 m. Find the height of the tree (in metres)
A tree breaks due to storm and the broken part bends, so that the top of the tree touches the ground making an angle of 30° with the ground. The distance between the foot of the tree to the point where the top touches the ground is 18 m. Find the height of the tree (in metres) Correct Answer 18√3
GIVEN:
BC = 18 m
CONCEPT:
FORMULAE USED:
Tanθ = Perpendicular/Base
Cosθ = Base/Hypotenuse
CALCULATION:
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Height of the tree = AB + AC
Tan 30° = AB/18
⇒ (1/√3) = AB/18
⇒ AB = (18/√3)
Cos 30° = BC/AC = 18/AC
⇒ √3/2 = 18/AC
⇒ AC = 36/√3
Hence, AB + AC = 18/√3 + 36/√3 = 54 / √3
⇒ 54/√3 × √3 /√3 (rationalizing to remove root from denominator)
⇒ 54√3 / 3 = 18√3
∴ Height of the tree = 18√3.
Mistake Point: Here, total height of tree is (AB + AC).
The above Question is previous year Question taken directly from NCERT class 10th. Correct answer will be 18√3