NCERT ex 10.4 ques 6..

Asked by harshitalohia | 27th Dec, 2009, 11:33: AM

Expert Answer:

Since they are sitting at equal distance on boundary, the lines joining the positions form an equilateral triangle, and hence the length of string of each phone will be the length of the equilateral triangle's side.

Also the line from the centre of circle and through any vertex will bisect the angle 60o/2.

so side of the equilateral triangle = 2(Rcos 30o) = 2x20x3/2 = 203 m.


where, R is the radius of the circle. And in cos 30o = Adjacent side/hypotenuse = adjacent side/R,

the triangle is OAB, O - centre of the circle, A - any vertex, OB perpendicular from the O onto side with one end A, and it bisetcts the side. OAB = 30o


This is also the length of telephone wire.




Answered by  | 27th Dec, 2009, 12:25: PM

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