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Sometimes a function of several real variables is written with a vector $\mathbf{x}=(x_1,x_2, \dots, x_n)$ such that $$ f(\mathbf{x})=f(x_1,x_2, \dots, x_n) $$

In linear algebra I learned that a vector is a vector in the form (with the standard basis) $$\mathbf{x}=(x_1,x_2, \dots, x_n)=x_1\mathbf{\hat{e}}_1+x_2\mathbf{\hat{e}}_2+\cdots + x_n\mathbf{\hat{e}}_n$$ Is this the same thing in multivariable calculus?

I.e. I mean is \begin{align} f(\mathbf{x})&=f(x_1\mathbf{\hat{e}}_1+x_2\mathbf{\hat{e}}_2+\cdots + x_n\mathbf{\hat{e}}_n)\\ &=f(x_1,x_2, \dots, x_n) \quad \text{?} \end{align}

  • 2
    Yes, that is correct. All you've done is rewritten $x$, three different ways.2017-02-18
  • 0
    True. The point is that $\hat{e}_1 = (1,0,0,\dots,0)$, etc.2017-02-18

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