A Polynomial Approximation

Problem

1. Prove that for x∈[0,1]x \in [0, 1],

22x⩽sin⁡x⩽x.\frac{\sqrt{2}}{2}x \leqslant \sin x \leqslant x.
  1. If the inequality
ax+x2+x32+2(x+2)cos⁡x⩽4ax + x^2 + \frac{x^3}{2} + 2(x+2)\cos x \leqslant 4

holds for all x∈[0,1]x \in [0, 1], find the range of possible values of the real number aa.

Answer

Solution

Difficulty6/10
Topicscalculus, Monotonicity, Estimation, inequality

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