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Question: Answered & Verified by Expert
If a1, a2, a3 are in arithmetic progression and d is the common difference, then tan-1 d1+a1a2+tan-1 d1+a2a3=
MathematicsInverse Trigonometric FunctionsJEE Main
Options:
  • A tan-1 2d1+a1a3
  • B tan-1 d1+a1a3
  • C tan-1 2d1+a2a3
  • D tan-1 2d1-a1a3
Solution:
2643 Upvotes Verified Answer
The correct answer is: tan-1 2d1+a1a3
Since, a1, a2, a3 are in A.P.

   a2-a1=d=a3-a2

Now, tan-1d1+a1a2+tan-1d1+a2a3

=tan-1a2-a11+a1a2+tan-1a3-a21+a2a3

tan1xtan1y=tan1xy1+xy

=tan-1a2-tan-1a1+tan-1a3-tan-1a2 

=tan-1a3-tan-1a1

=tan-1a3-a11+a1a3

=tan-1a3-a2+a2-a11+a1a3

=tan-12d1+a1a3

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