• 2022-06-19
    函数$f(x,y)=\sqrt{1+{{y}^{2}}}\cos x$在点$(0,1)$处的1次Taylor多项式为
    A: $\sqrt{2}-\frac{1}{\sqrt{2}}(y-1)$
    B: $\frac{\sqrt{2}}{2}+\frac{1}{\sqrt{2}(}y-1)$
    C: $2\sqrt{2}+\frac{1}{\sqrt{2}}(y-1)$
    D: $\sqrt{2}+\frac{1}{\sqrt{2}}(y-1)$