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In a triangle ABC, AB=AC and the length of the median from B to the side AC is 1. Find the cosine of the angle A for which the area of triangle is minimun.

In a triangle ABC, AB=AC and the length of the median from B to the side AC is 1. Find the cosine of the angle A for which the area of triangle is minimun.

Grade:12

1 Answers

Badiuddin askIITians.ismu Expert
148 Points
14 years ago

Dear harshit

 

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cosA =((b/2)2 +c2 -1) /bc

 

   b=c

 so   cos A = 5/4   -1/b2 

  b2=4/(5-4cosA)

 

nor area of triangle is =1/2 bc sinA

                              =1/2 b2 sinA

                              =2sinA/(5-4cosA)

now differntiate and value of cos A for minimum value of area


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