Heights and Distances
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HEIGHTS AND DISTANCES
In this chapter we learn how to use the trigonometric ratios to calculate heights of objects and distances between objects by measuring angles rather than sides.
ANGLE OF ELEVATION
Angle of elevation of a point P as observed from a point O (Refer figure) is the Angle POR where R is the foot of the perpendicular drawn from P to the horizontal plane through O. Thus, we can say that the angle of elevation is the angle between the line of sight and a particular horizontal line through the observer.
ANGLE OF DEPRESSION
Angle of depression of a point P as observed from a point O (Refer figure) is again the angle POR, R being the foot of the perpendicular drawn through O. Thus, the angle of depression is the angle between the line of sight and the
NOTE: The angle of elevation of one position as seen from the other is equal to the angle of depression of the latter as seen from the former.
COMPASS DIRECTIONS
The four directions North, South, East and West are at 90‚ to each other.
The four directions North-east, North-west, South-east and South-west are at 45‚ to the above.
The direction North of North-east (NNE) comes mid-way between N and NE. Similarly west of South-west (WSE) would be midway between W and SW.
When we say 30‚ East of North, we refer to a direction which makes 30‚ with the North and is towards the East (Refer figure5)