13.已知函数 $f(x)=\left\{\begin{array}{l}2 x^{3}, x<0, \\ -\tan x, 0 \leq x \leq \frac{\pi}{2},\end{array}\right.$ 则 $f\left(f\left(\frac{\pi}{4}\right)\right)=$
参考答案-2
2013_退役省自主命题 (2013·文)
13.已知函数 $f(x)=\left\{\begin{array}{l}2 x^{3}, x<0, \\ -\tan x, 0 \leq x \leq \frac{\pi}{2},\end{array}\right.$ 则 $f\left(f\left(\frac{\pi}{4}\right)\right)=$
[答案]-2
[解析]$f\left(\frac{\pi}{4}\right)=-\tan \frac{\pi}{4}=-1, \quad f(-1)=2 \cdot(-1)^{3}=-2$
[ 考点定位]对于分段函数的考查属容易题。