1.

f(x) = sin x - kx is decreasing for all x ∉ R, whenA. k < 1B. k ≤ 1C. k > 1D. k ≥ 1

Answer»

Answer is : D. k ≥ 1

f(x) = sin x - kx

f’(x) = cos x – k

∴ f decreases, if f’(x) ≤ 0

⇒ cos x – k ≤ 0

⇒ cos x ≤ k

So, for decreasing k ≥ 1.



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