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9.4 Defining and Differentiating Vector-Valued Functions

Part of Parametric Equations, Polar Coordinates, and Vector-Valued Functions in AP® Calculus BC. Read the opening section, then create a free account for the full interactive lesson, practice, and progress tracking.

A vector-valued function gives position in the plane or space using component functions. In two dimensions, it often looks like
r(t)=⟨x(t),y(t)⟩\mathbf{r}(t)=\langle x(t),y(t)\rangle
and in three dimensions,
r(t)=⟨x(t),y(t),z(t)⟩\mathbf{r}(t)=\langle x(t),y(t),z(t)\rangle
You differentiate a vector-valued function component by component, so
r′(t)=⟨x′(t),y′(t)⟩\mathbf{r}'(t)=\langle x'(t),y'(t)\rangle
or similarly in three dimensions. This derivative is often interpreted as velocity.

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