Sunita is an electrician and she has to repair an electric fault on a pole of height 5m.  She needs to reach to a point on the pole 1.3m below the top of the pole to undertake the repair work. What should be the length of ladder that she should use which, when inclined at an angle of 60° from the horizontal,  would she enable her to reach the required position ? Further how far from the foot of the pole should she place the foot of the ladder?  What value is indicated from this question? 

Asked by pdcavita | 19th Nov, 2017, 02:47: PM

Expert Answer:

 
 
begin mathsize 16px style Sunita space is space required space to space reach space the space point space straight B space on space the space pole space AD.
So comma space BD equals AD minus AB equals left parenthesis 5 minus 1.3 right parenthesis equals 3.7 space straight m
Let space BC space be space the space ladder.
In space triangle BDC comma
sin space 60 degree equals BD over BC
rightwards double arrow fraction numerator square root of 3 over denominator 2 end fraction equals fraction numerator 3.7 over denominator BC end fraction
rightwards double arrow BC equals fraction numerator 2 cross times 3.7 over denominator square root of 3 end fraction equals 4.27 space straight m
Now comma space cot space 60 degree equals CD over BD
rightwards double arrow fraction numerator 1 over denominator square root of 3 end fraction equals fraction numerator CD over denominator 3.7 end fraction
rightwards double arrow CD equals fraction numerator 3.7 over denominator square root of 3 end fraction equals 2.14 space straight m end style

Answered by Rashmi Khot | 30th Nov, 2017, 10:41: AM

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