一、选择题
1.若函数y =f (x )在x =a 处的导数为A ,则li m
Δx →0 f (a +Δx )-f (a -Δx )Δx
为( ) A .A
B .2A C.A 2 D .0 2.(2016·云南统一检测)函数f (x )=ln x -2x x
在点(1,-2)处的切线方程为( ) A .2x -y -4=0
B .2x +y =0
C .x -y -3=0
D .x +y +1=0
3.曲线y =ax cos x +16在x =π2
处的切线与直线y =x +1平行,则实数a 的值为( ) A .-2π
B.2π
C.π2 D .-π2
4.下面四个图象中,有一个是函数f (x )=13
x 3+ax 2+(
a 2
-1)x +1(a ∈R )的导函数y =f ′(x )的图象,则f (-1)等于( )
A.13
B .-23 C.73 D .-13或53
5.(2016·南昌二中模拟)设点P 是曲线y =x 3-3x +23
上的任意一点,则P 点处切线倾斜角α的取值范围为( )
A.????0,π2∪???
?5π6,π B.????2π3,π C.????0,π2∪????2π3,π D.????π2,5π6
6.(2016·昆明模拟)设f 0(x )=sin x ,f 1(x )=f ′0(x ),f 2(x )=f ′1(x ),…,f n +1(x )=f ′n (x ),n ∈N ,则f 2 015(x )等于( )
A .sin x
B .-sin x
C .cos x
D .-cos x
7.(2017·长沙调研)曲线y =13
x 3+x 在点???1,43处的切线与坐标轴围成的三角形面积为( ) A.29
B.19
C.13
D.23
8.若函数f (x )=cos x +2xf ′????π6,则f ????-π3与f ???
?π3的大小关系是( ) A .f ????-π3=f ???
?π3 B .f ????-π3>f ????π3 C .f ????-π3 ?π3 D .不确定 二、填空题 9.(2016·太原一模)函数f (x )=x e x 的图象在点(1,f (1))处的切线方程是____________. 10.已知函数f (x )=-f ′(0)e x +2x ,点P 为曲线y =f (x )在点(0,f (0))处的切线l 上的一点,点Q 在曲线y =e x 上,则|PQ |的最小值为________. 11.(2016·黄冈模拟)已知函数f (x )=x (x -1)(x -2)(x -3)(x -4)(x -5),则f ′(0)=________. 12.设曲线y =x n +1(n ∈N *)在点(1,1)处的切线与x 轴的交点的横坐标为x n ,则x 1·x 2·x 3·…·x 2 015=________. 答案精析 1.B [由于Δy =f (a +Δx )-f (a -Δx ), 其改变量对应2Δx , 所以0()()lim x f a x f a x x ?→+?--?? =0 ()()2lim 2x f a x f a x x ?→+?--?? =2f ′(a )=2A ,故选B.] 2.C [f ′(x )=1-ln x x 2 ,则f ′(1)=1,故函数f (x )在点(1,-2)处的切线方程为y -(-2)=x -1,即x -y -3=0.] 3.A [设y =f (x )=ax cos x +16,则f ′(x )=a cos x -ax sin x ,又因为曲线y =ax cos x +16在x =π2处的切线与直线y =x +1平行,所以f ′(π2)=-a π2=1?a =-2π ,故选A.] 4.D [∵f ′(x )=x 2+2ax +a 2-1, ∴f ′(x )的图象开口向上,则②④排除. 若f ′(x )的图象为①,此时a =0,f (-1)=53 ; 若f ′(x )的图象为③,此时a 2-1=0,又对称轴x =-a >0, ∴a =-1,∴f (-1)=-13 .] 5.C [因为y ′=3x 2-3≥-3,故切线斜率k ≥-3, 所以切线倾斜角α的取值范围是????0,π2∪??? ?2π3,π.] 6.D [∵f 0(x )=sin x ,f 1(x )=cos x , f 2(x )=-sin x ,f 3(x )=-cos x ,f 4(x )=sin x ,…, ∴f n (x )=f n +4(x ),故f 2 012(x )=f 0(x )=sin x , ∴f 2 015(x )=f 3(x )=-cos x ,故选D.]