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2.1 Vector-Valued Functions and Space Curves

2 min readjuly 25, 2024

take us beyond single values, outputting vectors instead. They're like a GPS for math, giving us x, y, and z coordinates all at once. These functions help us map out paths in 3D space, tracing curves like helixes and circles.

Graphing these functions is like connecting the dots in three dimensions. We plot points, figure out which way the curve's going, and join them up. The tells us what inputs work, while the shows all possible outputs. It's like setting the boundaries for our mathematical playground.

Vector-Valued Functions

Concept of vector-valued functions

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  • Functions output vectors instead of scalar values, typically denoted as r(t)=f(t),g(t),h(t)\mathbf{r}(t) = \langle f(t), g(t), h(t) \rangle
  • Components include xx-component f(t)f(t), yy-component g(t)g(t), and zz-component h(t)h(t)
  • uses a parameter (usually tt) to define each component
  • Each as a scalar-valued function, mapping parameter to real number

Representation of space curves

  • trace paths in three-dimensional space using vector-valued functions
  • define space curves: x=f(t)x = f(t), y=g(t)y = g(t), z=h(t)z = h(t)
  • Vector form expresses space curves as r(t)=f(t)i+g(t)j+h(t)k\mathbf{r}(t) = f(t)\mathbf{i} + g(t)\mathbf{j} + h(t)\mathbf{k}
  • Common space curves include:
    • : r(t)=cost,sint,t\mathbf{r}(t) = \langle \cos t, \sin t, t \rangle spirals around z-axis
    • : r(t)=cost,sint,0\mathbf{r}(t) = \langle \cos t, \sin t, 0 \rangle traces unit circle in xy-plane

Graphing and Analysis

Graphs of vector-valued functions

  • Sketching techniques:
    1. Plot individual points for different tt values
    2. Identify curve's and
    3. Connect points to form continuous curve
  • Special cases:
    • confined to single plane (ellipse)
    • return to starting point (circle)
  • :
    • plot 3D curves
    • Computer software (Mathematica, MATLAB) generates interactive 3D models

Domain and range in vector functions

  • Domain considers interval of tt where all component functions are defined
  • Restrictions based on physical context limit domain (time cannot be negative)
  • Range analysis determines set of all possible output vectors
  • of range as set of points traced by curve
  • Finding domain and range:
    • Examine each component function separately
    • Consider intersections of individual domains
  • Special cases affect range:
    • Periodic functions create repeating patterns (sine wave)
    • Bounded ranges have limits (unit circle)
    • Unbounded ranges extend infinitely (spiral)
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© 2024 Fiveable Inc. All rights reserved.
AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.

© 2024 Fiveable Inc. All rights reserved.
AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.
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