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Home » An electrician has to repair an electric fault on a pole of height 4 meters. He needs to reach a point 1 meter 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 to the horizontal would enable him to reach the required position?
An electrician has to repair an electric fault on a pole of height 4 meters. He needs to reach a point 1 meter 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^{\circ} to the horizontal would enable him to reach the required position?
CBSE | Class 10 | Maths | RS Aggarwal | Some Applications Of Trigonometry
An electrician has to repair an electric fault on a pole of height 4 meters. He needs to reach a point 1 meter 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^{\circ} to the horizontal would enable him to reach the required position?

Let \mathrm{AC} be the pole and \mathrm{BD} be the ladder We have,

\mathrm{AC}=4 \mathrm{~m}, \mathrm{AB}=1 \mathrm{~m} and \angle \mathrm{BDC}=60^{\circ}

And, B C=A C-A B=4-1=3 m

In \triangle B D C

\sin 60^{\circ}=\frac{\mathrm{BC}}{\mathrm{BD}}

\Rightarrow \frac{\sqrt{3}}{2}=\frac{3}{\mathrm{BD}}

\Rightarrow \mathrm{BD}=\frac{3 \times 2}{\sqrt{3}}

\Rightarrow \mathrm{BD}=2 \sqrt{3}

\Rightarrow \mathrm{BD}=2 \times 1.73

\therefore \mathrm{BD}=3.46 \mathrm{~m}

=>he should use 3.46 \mathrm{~m} long ladder to reach the required position.

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