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Question: Answered & Verified by Expert
If x, y, z are in arithmetic progression and tan-1x,tan-1y and tan-1z are also in arithmetic progression, then
MathematicsInverse Trigonometric FunctionsJEE Main
Options:
  • A x=y=z
  • B x=y=-z
  • C x=1, y=2, z=3
  • D x=2, y=4, z=6
Solution:
1830 Upvotes Verified Answer
The correct answer is: x=y=z
Since, x, y, z are in AP

∴   y=x+z2    ....(i)

And tan-1x,tan-1y and tan-1z are also in AP.

∴   2tan-1y=tan-1x+tan-1z

⇒   tan-12y1-y2=tan-1x+z1-xz

⇒   2y1-y2=2y1-xz    [from equation. (i)]

⇒   y2=xz

⇒   x, y, z are in GP.

∴   x=y=z

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