Question:
In Fig. 12.58, what are the angles of depression from the observing position O1 and O2 of the object at A?
Solution:
In a triangle
,
$\Rightarrow \angle A=180^{\circ}-\left(90^{\circ}+60^{\circ}\right)$
$\Rightarrow \angle A=180^{\circ}-150^{\circ} \quad$ We know that $\left[\angle A+\angle B+\angle C=180^{\circ}\right]$
$\Rightarrow \angle A=30^{\circ}$
Again,
In a triangle
,
$\Rightarrow \angle O_{2}=180^{\circ}-\left(90^{\circ}+45^{\circ}\right)$
$\Rightarrow \angle O_{2}=180^{\circ}-135^{\circ}$
$\Rightarrow \angle O_{2}=45^{\circ}$
Hence the required angles are $30^{\circ}, 45^{\circ}$.