01 · KEY DEFINITIONS
Core Concepts & Terminology
Line of Sight
Line of Sight
The straight line drawn from the eye of an observer to the object viewed.Elevation
Angle of Elevation
The angle formed by the line of sight with the horizontal line when looking UPWARD (object above horizontal level).Depression
Angle of Depression
The angle formed by the line of sight with the horizontal line when looking DOWNWARD (object below horizontal level).GEOMETRIC DIAGRAM
Angle of Elevation vs Angle of Depression
Key Property: Angle of Elevation = Angle of Depression (Alternate Interior Angles)
02 · RATIOS TO USE
Selecting the Right Ratio
In right-angled triangle problems:
tan θ = Opposite (Height) / Adjacent (Distance)sin θ = Opposite (Height) / Hypotenuse (Slant Length / String)cos θ = Adjacent (Distance) / Hypotenuse (Slant Length)
03 · QUICK SUMMARY
Key Takeaways
01
Always draw a clear right triangle diagram first!
02
Angle of elevation = Angle of depression because horizontal lines are parallel.
03
tan 30° = 1/√3, tan 45° = 1, tan 60° = √3 (Most frequently used values!).