Guy wire to a 20 m pole: A 20 m vertical electric pole is anchored to the ground by a wire attached to its top. If the wire makes a 60° angle with the horizontal ground, find the length of the wire.

Difficulty: Easy

Correct Answer: 40/ √3 m

Explanation:


Introduction / Context:
The wire forms the hypotenuse of a right triangle with the ground (adjacent) and the pole (opposite). The angle given is with the horizontal, so use sine to relate opposite and hypotenuse.


Given Data / Assumptions:

  • Pole height = 20 m.
  • Angle with ground = 60°.


Concept / Approach:
sin θ = opposite / hypotenuse → hypotenuse = opposite / sin θ.


Step-by-Step Solution:

Wire length L = 20 / sin 60° = 20 / (√3/2) = 40/√3 m.


Verification / Alternative check:
Numeric: √3 ≈ 1.732 → L ≈ 23.094 m; geometry consistent with a steep wire.


Why Other Options Are Wrong:
40√3 is too long (would imply sin 60° < 0.5); 20√3 and 20/√3 arise from mixing cosine or tangent incorrectly.


Common Pitfalls:
Using cos instead of sin since angle is with ground; rationalizing incorrectly; forgetting the 1/2 factor in sin 60°.


Final Answer:
40/ √3 m

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