Q47 / 90 · JEE Main 2016 (09 Apr Online) · Mathematics

In a triangle ABC, right angle at vertex A, if the position vectors of A,B and C are respectively 3i^+ j^- k^, -i^+3j^+pk^ and 5i^+qj^-4k^ , then the point p,q lies on a line:

  • A
    Making an obtuse angle with the positive direction of x-axis
  • B
    Parallel to x-axis
  • C
    Parallel to y-axis
  • Correct answer
    D
    Making an acute angle with the positive direction of x-axis

Solution

Figure

AB→= -4i^+2j^+p+1k^

AC→= 2i^+q-1j^-3k^

AB→⊥AC→

⇒ AB→ · AC→=0

-8+2q-1-3p+1=0

3p-2q+13=0

p,q lies on 3x-2y+13=0

Slope =32

∴  The required line makes an acute angle with the positive direction of x-axis.

Hence, the correct answer is option: 'D'.

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