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JEE Mains · Maths · STD 11 - 8. sequence and series

If \(x,y,z\)  are in \(A.P.\) and  \({\tan ^{ - 1}}x,{\tan ^{ - 1}}y\) and \({\tan ^{ - 1}}z\) are also in other \(A.P.\) then  . . . 

  1. A \(x = y = z\)
  2. B \(x = y = - z\)
  3. C \(x = 1;y = 2;z = 3\)
  4. D \(x = 2;y = 4;z = 6\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(x = y = z\)

Step-by-step Solution

Detailed explanation

\(2 y=x+z\) ....\((1)\) As \(\tan ^{-1} x, \tan ^{-1} y, \tan ^{-1} z\) in \(A.P\) \(\Rightarrow 2 \tan ^{-1} y=\tan ^{-1} \frac{x+z}{1-x z}\) \(\frac{2 y}{1-y^{2}}=\frac{x+z}{1-x z}\) \(\frac{x-z}{1-y^{2}}=\frac{x+z}{1-x z}\) by \(( 1)\)…