1.已知$a = \text{e}^{- \frac{1}{2}}\sin\frac{1}{2}$,$b = \frac{1}{2}\text{e}^{- \frac{\text{π}}{6}}$,$c = \frac{\sqrt{2}}{2}\text{e}^{- \frac{\text{π}}{4}}$,则( )
A.$c > b > a$ B.$a > b > c$ C.$b > a > c$ D.$c > a > b$
解 令$f(x) = \text{e}^{x}\sin( - x) = - \text{e}^{x}\sin x$,则$f'(x) = - \text{e}^{x}\sin x - \text{e}^{x}\text{cos}x = - \sqrt{2}\text{e}^{x}\sin\left( x + \frac{\text{π}}{4} \right)$,
当$- \frac{\text{π}}{4} < x < 0$时,$\sin\left( x + \frac{\text{π}}{4} \right) > 0$,$\text{e}^{x} > 0$,则$f'(x) < 0$,所以$f(x)$在$\left( - \frac{\text{π}}{4},0 \right)$上单调递减,则$f(x) < f\left( - \frac{\text{π}}{4} \right)$,
因为$0 < \frac{1}{2} < \frac{\text{π}}{6} < \frac{\text{π}}{4}$,所以$0 > - \frac{1}{2} > - \frac{\text{π}}{6} > - \frac{\text{π}}{4}$,
所以$f\left( - \frac{1}{2} \right) < f\left( - \frac{\text{π}}{6} \right) < f\left( - \frac{\text{π}}{4} \right)$,
即$\text{e}^{- \frac{1}{2}}\sin\frac{1}{2} < \text{e}^{- \frac{\text{π}}{6}}\sin\frac{\text{π}}{6} < \text{e}^{- \frac{\text{π}}{4}}\sin\frac{\text{π}}{4}$,则$\text{e}^{- \frac{1}{2}}\sin\frac{1}{2} < \frac{1}{2}\text{e}^{- \frac{\text{π}}{6}} < \frac{\sqrt{2}}{2}\text{e}^{- \frac{\text{π}}{4}}$,故$a < b < c$,
所以$c > b > a$,故选:A.
2.设$a = \text{e}^{0.02} - 1$,$b = 2\left( \text{e}^{0.01} - 1 \right)$,$c = \sin 0.01 + \tan 0.01$,则( )
A.$a > b > c$ B.$a > c > b$
C.$c > a > b$ D.$b > c > a$
解 因为$a - b = \text{e}^{0.02} - 2\text{e}^{0.01} + 1 = \left( \text{e}^{0.01} - 1 \right)^{2} > 0$,所以$a > b$.
设$f(x) = 2\left( \text{e}^{x} - 1 \right) - \sin x - \tan x$,
则$f'(x) = 2\text{e}^{x} - \cos x - \frac{1}{\cos^{2}x}$,
令$g(x) = f'(x)$,则$g'(x) = 2\text{e}^{x} + \sin x - \frac{2\sin x}{\cos^{3}x}$.
当$x \in \left( 0,\frac{\text{π}}{6} \right)$时,$2\text{e}^{x} > 2$,$\sin x > 0$,$\frac{2\sin x}{\cos^{3}x} < \frac{2\sin\frac{\text{π}}{6}}{\cos^{3}\frac{\text{π}}{6}} = \frac{8\sqrt{3}}{9} < 2$,
所以$g'(x) > 0$,所以当$x \in \left( 0,\frac{\text{π}}{6} \right)$时,$f'(x) > f'(0) = 0$,
所以$f(x)$在$x \in \left( 0,\frac{\text{π}}{6} \right)$上单调递增,
从而$f(x) > f(0) = 0$,
因此$f(0.01) > 0$,即$b > c$.
综上可得$a > b > c$.故选:A