InterviewSolution
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InterviewSolution
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The equation `x^3=3/4x=-(sqrt(3))/8`is satisfied by`x=cos((5pi)/(18))`(b) `x=cos((7pi)/(18))``x=cos((23pi)/(18))`(d) `x=cos((17pi)/(18))`A. `x=cos((5pi)/(18))`B. `x =cos((7pi)/(18))`C. `x=cos((23pi)/(18))`D. `x=-sin((7pi)/(9))` |
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Answer» Correct Answer - A::B Let `x = cos theta` `rArr 4 cos^(3) theta -3 cos. theta =-(sqrt(3))/(2)` `rArr cos 3 theta = cos.(5pi)/(6)` `rArr 3 theta = 2n pi pm (5pi)/(6), n in Z` `rArr theta =(2n pi)/(3)pm(5pi)/(18),, n in Z` Put `n=0, theta =(5pi)/(18)` `n=1, theta =(2pi)/(3)+(5pi)/(18)=(17pi)/(18)` `theta =(2pi)/(3)-(5pi)/(18)=(7pi)/(18)` |
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