JEE 2014 Advanced Mathematics Paper

49. From a point P(lambda, lambda, lambda), perpendiculars PQ and PR are drawn respectively on the lines
y = x,  z = 1 and y  = -x and  z = − 1. If P is such that ∠QPR is a right angle, then the possible
value(s) of lambda is (are)
A) SQRT (2) B) 1         C) -1           D) − SQRT (2)

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