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WBJEE · Maths · Straight Lines

Consider three points \(P(\cos \alpha, \sin \beta), Q(\sin \alpha, \cos \beta), R(0,0)\), where \(0 \lt \alpha, \beta \lt \frac{\pi}{4}\). Then

  1. A \(P\) lies on the line segment RQ
  2. B Q lies on the line segment PR
  3. C \(R\) lies on the line segment \(P Q\)
  4. D P, Q, R are non-collinear
Verified Solution

Answer & Solution

Correct Answer

(D) P, Q, R are non-collinear

Step-by-step Solution

Detailed explanation

\begin{aligned} & \text {Consider } \Delta=\left|\begin{array}{ccc} \cos \alpha & \sin \beta & 1 \\ \sin \alpha & \cos \beta & 1 \\ 0 & 0 & 1 \end{array}\right| \\ & =\cos \alpha \cos \beta-\sin \alpha \sin \beta \\ & =\cos (\alpha+\beta) \neq 0 \text { as } 0 < \alpha+\beta <…