已知由方程siny+xey=0,确定y是x的函数,则dy/dx的值是:()
A.-(ey+cosy)/xey B.-ey/cosy C.-ey/(cosy+xey) D.-cosy/xey
设参数方程,确定了y是x的函数,f″(t)存在且不为零,则d2y/d2x的值是:()
A.-1/f″(t) B.1/[f″(t)]2 C.-1/[f″(t)]2 D.1/f″(t)
(x+ex)的值是:()
A.e B.e C.1 D.2