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Question: Answered & Verified by Expert
The value of \( k \) in order that \( f(x)=\sin x-\cos x-k x+b \) decreases for all real values is given by:
MathematicsApplication of DerivativesJEE Main
Options:
  • A \( k < 1 \)
  • B \( k>1 \)
  • C \( k>\sqrt{2} \)
  • D \( k < \sqrt{2} \)
Solution:
2650 Upvotes Verified Answer
The correct answer is: \( k>\sqrt{2} \)

Given:

fx=sinx-cosx-kx+bf'x=cosx+sinx-k

For decreasing function f'x < 0

So, cos x + sin x - k < 0

The maximum value of cos x + sin x is 2.

2-k<0

k>2

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