Line of sight
The line of sight is the straight line joining the observer's eye to the object being seen.
In one line: Sight line means the straight line your eyes follow to the object.
Practice This ConceptUnderstand it
- In trigonometry problems, the line of sight is the slant line that connects the observer and the target object.
- It is the key line used to form the angle of elevation or depression.
- Without this line, we cannot build the right triangle needed for height and distance questions.
- The line of sight is always straight, not curved, because we imagine the shortest viewing path.
Example
Formula and rule
Line of sight is the straight slant line from eye to object; it helps create the right triangle for trigonometric ratios.
See it worked out
Follow the example line by line, then use the same method on new questions.
Worked example
- 1A person standing on the ground sees the top of a tree.
- 2The straight segment from the eye to the top of the tree is the line of sight, and together with the horizontal and vertical it forms a right triangle.
Method you can reuse
- 1Mark the observer's eye.
- 2Mark the target object point.
- 3Join them with a straight slant line.
- 4Label that line as the line of sight.
- 5Use it with the horizontal to form the angle.
Sketch it in your answer
Draw a straight slant segment from the observer's eye to the top or target point of the object. Label it clearly as line of sight.
Check yourself
Answer the question in your head before opening the answer.
Try it yourself
In a height-and-distance problem, what does the line of sight connect?
Think first, then show answerHide answer
Common wrong answer
A common wrong answer is to treat the ground distance as the line of sight. The ground distance is only the adjacent side, not the viewing line.
Don't mix this up
Exam tip
Write it in the exam
Each point is worth about one mark. Write point 1 for a 1-mark question and keep adding points as the marks go up.
How CBSE asks it
- 1
Enough for 1 mark
The line of sight is the straight line joining the observer's eye to the object being seen.
- 2
Add for 2 marks
In trigonometry problems, the line of sight is the slant line that connects the observer and the target object.
- 3
Add for 3 marks
It is the key line used to form the angle of elevation or depression.
Practice this concept with focused MCQs
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