Answer
64.8k+ views
Hint: Draw the diagram of the given problem statement for a better understanding of the situation. Use the trigonometric ratios, that are $\sin \theta = \dfrac{{{\text{Opposite}}}}{{{\text{Hypotenuse}}}}$ and $\tan \theta = \dfrac{{{\text{Perpendicular}}}}{{{\text{Base}}}}$ in the physical triangle formed to find the height of the tower.
Complete step by step answer:
Let us assume the point at a foot distant from the tower be $P$.
We can draw the figure for the given scenario, where the flagstaff is fixed on the top of the tower, which is a foot distant from $P$.
The point $P$ lies in the plane of the bottom of the tower. The angle of elevation from point P to the top of the flag staff is $\alpha $ and angle of elevation from the point $P$ to the bottom of the flag staff is $\beta $.
![](https://www.vedantu.com/question-sets/93c4424c-0cc3-49f2-b35b-3286f75d97241759130048222442256.png)
Here $BC$ represents the height of the tower and $AB$ represents the height of the flag staff.
From the figure, in the triangle $PBC$
$\tan \beta = \dfrac{{BC}}{{PC}}$
Substituting $a$ for \[PC\] we get
$\tan \beta = \dfrac{{BC}}{a}$
On simplifying, we get
$a\tan \beta = BC$
Here $BC$ represents the height of the tower, therefore, the height of the tower is $a\tan \beta $.
Thus option D i.e. none of these is the correct answer.
Note: The diagram should be drawn correctly according to the given conditions correctly. The angle of elevation of a higher point is more than that for a lower point in the same vertical line. In a right angled triangle, the $\tan \theta $ is the equal to $\dfrac{{{\text{Perpendicular}}}}{{{\text{Base}}}}$, where perpendicular is the side opposite to the angle $\theta $, and $\sin \theta $ is the equal to $\dfrac{{{\text{Perpendicular}}}}{{{\text{Hypotenuse}}}}$, where perpendicular is the side opposite to the angle $\theta $.
Complete step by step answer:
Let us assume the point at a foot distant from the tower be $P$.
We can draw the figure for the given scenario, where the flagstaff is fixed on the top of the tower, which is a foot distant from $P$.
The point $P$ lies in the plane of the bottom of the tower. The angle of elevation from point P to the top of the flag staff is $\alpha $ and angle of elevation from the point $P$ to the bottom of the flag staff is $\beta $.
![](https://www.vedantu.com/question-sets/93c4424c-0cc3-49f2-b35b-3286f75d97241759130048222442256.png)
Here $BC$ represents the height of the tower and $AB$ represents the height of the flag staff.
From the figure, in the triangle $PBC$
$\tan \beta = \dfrac{{BC}}{{PC}}$
Substituting $a$ for \[PC\] we get
$\tan \beta = \dfrac{{BC}}{a}$
On simplifying, we get
$a\tan \beta = BC$
Here $BC$ represents the height of the tower, therefore, the height of the tower is $a\tan \beta $.
Thus option D i.e. none of these is the correct answer.
Note: The diagram should be drawn correctly according to the given conditions correctly. The angle of elevation of a higher point is more than that for a lower point in the same vertical line. In a right angled triangle, the $\tan \theta $ is the equal to $\dfrac{{{\text{Perpendicular}}}}{{{\text{Base}}}}$, where perpendicular is the side opposite to the angle $\theta $, and $\sin \theta $ is the equal to $\dfrac{{{\text{Perpendicular}}}}{{{\text{Hypotenuse}}}}$, where perpendicular is the side opposite to the angle $\theta $.
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