An electrician has to repair an electric fault on a pole of height 4 metres. He needs to reach a point 1 metre below the top of the pole to undertake the repair work. What should be the length of the ladder that he should use, which when inclined at an angle of 60° to the horizontal would enable him to reach the required position? [Use √3 = 1.73.]

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Let AB be the pole and D be the 1m below A. The person needs to reach the point D. So, BD = 3m. Let DC be the ladder. Join D and C. We get a right-angled triangle ∆DBC, right angled at B. The angle of elevation of the ladder, ∠BCD = 60°. We use trigonometric ratio sin, using DC as hypotenuse and DB as height to find the length of the ladder DC.


In ∆BDC,



or,



Hence, the length of the ladder will be 3.46m.


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