99 Percentile Qs Bank for JEE MainMathematicsThree Dimensional Geometry

If the angle between the lines whose direction cosines are (- 2 21 , C 21 , 1 21 ) and ( 3 54 , 3 54 ,- 6 54 ) is 2 , then the value of C is

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Correct answer

B. 4

Step-by-step solution

Given, aligned & I₁=- 2 21 , m₁= C 21 , n₁= 1 21 & and l₂= 3 54 , m₂= 3 54 , n₂= -6 54 & =l₁ 1₂+m₁ m₂+n₁ n₂ & & 2 =- 2 21 3 54 + C 21 3 54 + 1 21 - 6 54 & 0= -6 21 54 + 3 C 21 54 - 6 21 54 & 12 21 54 = 3 C 21 54 & 3 C =12 & C=4 & aligned

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