Question

A triangle have sides x cm, 8cm and (x+2)cm, where x>6. If the cosine of the largest angle of the triangle is 2/7 calculate the value of x 2/7
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Answer 1

Given sides of triangle, a=2cm,b=8cm,c=9cm 

cosine law 

cosA=2bcb2+c2−a2

cosB=aca2+c2−b2

cosC=2abb2+a2−c2

cosA=(2)(8)(9)82+92−22=144141

cosB=(2)(2)(8)22+92−82=3621

cosC=(2)(2)(8)82+22−92=