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AP EAMCET202124 Aug 2021Evening ShiftMathematicsVector AlgebraActual

Let a , b and c be the three vectors. If | a |=1 , | b |=17 and | c |=8 and the angle between a and b is and a ( a b )- c =0 , then + cosec is equal to

Options

  1. A409 136
  2. B309 136
  3. C419 126
  4. D409 126

Correct answer

A. 409 136

Step-by-step solution

Given, | a |=1,| b |=17 and | c |=8 Angle between a and b is . a ( a b )- c =0 array lc & a ( a b )= c & | a ( a b )|=| c | array | a | a || b | 90^ =| c |[ a is perpendicular to a b ] | a |^2| b | =| c | = | c | | a |^2| b | = 8 1 17 = 8 17 = 1- ( 8 17 )^2 = 15 17 + cosec = 15 17 + 17 8 = 120+289 136 = 409 136

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