JEE Advanced 2014 Mathematics question

From a point P(λ, λ, λ), perpendiculars PQ and PR are drawn respectively on the lines y = x, z = 1 and y = −x, z = −1. If P is such that ∠QPR is a right angle, then the possible value(s) of λ is(are)

(A)
(B)1
(C)−1Correct
(D)

Answer: (C)

Solution

First line: points (t, t, 1), direction (1, 1, 0). is perpendicular to (1, 1, 0) when t = λ, so Q = (λ, λ, 1). Second line: points (s, −s, −1), direction (1, −1, 0): , so R

See the full step-by-step solution

Create a free account to read the complete working, and practise questions like this in a timed test.

Create a free account

Question ID VK-026290