AP EAMCET2008MathematicsThree Dimensional Geometry

The angle between the lines whose direction cosines are ( 3 4 , 1 4 , 3 2 ) and ( 3 4 , 1 4 , - 3 2 ) , is

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Correct answer

C. 4

Step-by-step solution

Given that, l₁= 3 4 , m₁= 1 4 and n₁= 3 2 and l₂= 3 4 , m₂= 1 4 and n₂= - 3 2 aligned & = |l₁ l₂+m₁ m₂+n₁ n₂ | & = | 3 4 3 4 + 1 4 1 4 + 3 2 ( - 3 2 ) | & = | 3 16 + 1 16 - 3 4 |= |- 2 4 |= 1 2 & = 3 aligned

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