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Booklet Question: For safety, the angle between a ladder and the ground should be between 60 and 78. A ladder 8m in length is placed 3m from the base of a wall. Is it safe to climb the ladder?

My Question: What confuses me is the angle being inbetween 60-78?
 Sep 12, 2013

2+0 Answers

 #1
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My Question: What do you mean by 'What confuses me is the angle being inbetween 60-78?'?
 Sep 12, 2013
 #2
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length of the ladder is the hypotenuse: H = 8m
The distance is the adjacent side: A = 3m
So we've got the equation: cos(a) = A/H
a = arccos(A/H)

This has to be between 60° and 78°: 60° < a < 78°
a = arccos(A/H) = arccos(3m/8m) = 67.98°

60° < 67.98° < 78° ✔
 Sep 12, 2013

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