InterviewSolution
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InterviewSolution
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Let `0lt=a , b , c ,dlt=pi,`where `ba n dc`are not complementary, such that `2cosa+6cosb+7cosc+9cosd=0a n d2sina-6sinb+7sinc-9a n dd=0,`then the value of `3(cos(a+d))/("cos"(b+c))`is_____ |
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Answer» Correct Answer - 7 From the given equations, we have ` " " (2 cos a + 9 cos d)^(2) = (6 cos b + 7 cos c)^(2) ` `and ( 2 sin a - 9 sin d)^(2) = (6 sin b - 7 sin c )^(2)` Adding, we have `36 cos (a+d) = 84 cos (b+c)` or `(cos(a+d))/(cos (b+c)) = (7)/(3)` |
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