JEE Main2016MathematicsThree Dimensional GeometryActual
A B C is a triangle in a plane with vertices A 2 , 3 , 5 , B - 1 , 3 , 2 and C λ , 5 , μ . If the median through A is equally inclined to the coordinate axes, then the value of λ 3 + μ 3 + 5 is
Options
- A1130
- B1348
- C1077
- D676
Correct answer
B. 1348
Step-by-step solution
Let coordinate of mid-point of B C is point D , then D ≡ λ - 1 2 ,   4 ,   μ + 2 2 And, A ≡ 2 , 3 , 5 Therefore, direction ratios of A D are λ - 1 2 - 2 ,   4 - 3 , μ + 2 2 - 5 λ - 5 2 ,   1 , μ - 8 2 Hence, direction cosines of A D are λ - 5 2 λ - 5 2 2 + 1 + μ - 8 2 2 ,   1 λ - 5 2 2 + 1 + μ - 8 2 2 , μ - 8 2 λ - 5 2 2 + 1 + μ - 8 2 2 Since, median A D is making equal angles with coordinate axes, therefore &