Answers

2015-03-25T10:11:29+05:30
sin{(1/2)[cos-inverse (4/5)]} = sin{(1/2)[36.87]} = 
sin{(1/2)[cos-inverse (4/5)]} = sin(18.435) = 
sin{(1/2)[cos-inverse (4/5)]} = 0.31623 = Answer
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2015-03-25T11:51:42+05:30
  Since sin(x/2) = √((1 - cos(x))/2) 

sin(arccos(4/5)/2) = √((1 - cos(arccos(4/5)))/2)
                           = √((1 - (4/5))/2)
                            = 1/√(10).
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