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Question: Answered & Verified by Expert
If 2tan-1cosx=tan-1(2coscex) then sinx+cosx=
MathematicsInverse Trigonometric FunctionsMHT CETMHT CET 2016
Options:
  • A 22
  • B 2
  • C 12
  • D 12
Solution:
2873 Upvotes Verified Answer
The correct answer is: 2
As given, 2tan-1 cos x=tan-1 (2cosce x)
tan-1 cos x+tan-1 cos x=tan-1 (2cosce x)
Since cos x 1
=tan-1 2cos x1-cos2 x=tan-1 (2cosce x)
  2cos xsin2 x=2cosce x
 2cot x=2
 cot x=1
 x=π4
Hence,
sin x+cos x=sinπ4+cosπ4
=12+12
=2

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