The range of for which the inequality is:

MATHEMATICS · Single correct · CBSE · Mathematics · Trigonometric Functions · Trigonometric Functions

Problem

The range of kk for which the inequality kcos⁡2x−kcos⁡x+1≥0∀x∈(−∞,∞)k \cos^2 x - k \cos x + 1 \ge 0 \forall x \in (-\infty, \infty) is: (a) k>−12k > -\frac{1}{2} (b) k>4k > 4 (c) −12≤k≤4-\frac{1}{2} \le k \le 4 (d) 12≤k≤5\frac{1}{2} \le k \le 5

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