Straight Line and Pair of Straight Lines 2 Question 2

2. Consider three points

P=sin(βα)cosβ,Q=cos(βα),sinβ

and R=cos(βα+θ)sin(βθ),

where 0<α,β,θ<π4. Then,

(2008,4M)

(a) P lies on the line segment RQ

(b) Q lies on the line segment PR

(c) R lies on the line segment QP

(d) P,Q,R are non-colinear

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Answer:

Correct Answer: 2. (d)

Solution:

  1. For collinear points

Δ=|sin(βα)cosβ1cos(βα)sinβ1cos(βα+θ)sin(βθ)1|

Clearly, Δ0 for any value of α,β,θ.

Hence, points are non-collinear.



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