设y=xtanx，则y'=

A 0 B <img src="https://www.beizhujiaoyu.com/uploads/202208/164679054357251.png" width="15" height="31" />  C 1 D 2

A ex+cosx B ex-cosx C ex-sinx D ex+sinx

A <img src="https://www.beizhujiaoyu.com/uploads/202208/164679056524561.png" width="83" height="32" />  B <img src="https://www.beizhujiaoyu.com/uploads/202208/164679057055931.png" width="83" height="33" />  C <img src="https://www.beizhujiaoyu.com/uploads/202208/164679057618171.png" width="64" height="32" />  D <img src="https://www.beizhujiaoyu.com/uploads/202208/164679058527711.png" width="64" height="33" /> 

A (0，0) B (0。1) C (-1，0) D (1，1)

A -sin2x B sin2x C -2sin2x D 2sin2x

A -2 B -l C 1 D 2

A -6ycos(x-3y2) B -6ysin(x-3y2) C 6ycos(x-3y2) D 6ysin(x-3y2)

A xf”(x2+y) B 2xf”(x2+y) C yf”(x2+y) D 2xyf”(x2+y)

A 0．4 B 0．5 C 0．7 D 0．9