Show that Vector function lies on a sphere

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SUMMARY

The discussion centers on proving that a differentiable 3-space vector-valued function r lies on a sphere centered at the origin if and only if r(t) and r′(t) are orthogonal for all t. The key equation derived is ||r(t)|| = C, indicating that the magnitude of r(t) is constant. The proof requires demonstrating both necessary and sufficient conditions, emphasizing the importance of the dot product in establishing orthogonality between r(t) and its derivative r′(t).

PREREQUISITES
  • Differentiable vector-valued functions in 3-space
  • Understanding of dot products and orthogonality
  • Concept of constant magnitude in vector functions
  • Basic principles of calculus, particularly differentiation
NEXT STEPS
  • Study the properties of differentiable vector-valued functions
  • Learn about the geometric interpretation of dot products
  • Explore the implications of constant magnitude in vector calculus
  • Investigate proofs involving necessary and sufficient conditions in mathematics
USEFUL FOR

Students and educators in calculus, particularly those focusing on vector calculus and geometric interpretations, as well as anyone interested in understanding the relationship between vector functions and their geometric properties.

karens
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Homework Statement



Let r1 and r2 be differentiable 3-space vector-valued functions.

Show that for a differentiable 3-space vector-valued function r, the graph of r lies on a sphere centered at the origin if and only if r(t) and r′(t) are orthogonal (perpendicular) for all t.

Homework Equations



Dot products?

The Attempt at a Solution


If R(t) is on the surface of such a sphere then ||R(t)||=C, is constant.
 
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so, if i;m interpreting this correctly if ||r(t)||=c, then you could write it as:

[tex]\textbf{r}(t) \bullet \textbf{r}(t) = c^2[/tex]
how about differentiating...

note that as the question has "if & only if" you must show both directions, necessary & sufficient" to complete the proof
 

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