Shadow equal to height: When the length of the shadow of a vertical pole equals the height of the pole on level ground, what is the angle of elevation of the light source?

Difficulty: Easy

Correct Answer: 45°

Explanation:


Introduction / Context:
Relating a pole, its shadow, and the angle of elevation uses basic trigonometry: tan θ = opposite/adjacent = height/shadow length.


Given Data / Assumptions:

  • Height = shadow length.
  • Level ground; vertical pole.


Concept / Approach:
tan θ = height/shadow = 1 → θ = 45°.


Step-by-Step Solution:

Let height = h and shadow = h.tan θ = h / h = 1 → θ = 45°.


Verification / Alternative check:
In a 45°-45°-90° triangle, legs are equal; consistent with the condition.


Why Other Options Are Wrong:
30° or 60° would give unequal legs (shadows √3 h or h/√3), not equal lengths.


Common Pitfalls:
Using sine or cosine instead of tangent; misreading “shadow equals height”.


Final Answer:
45°

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