Prove Vector Derivative (using Dot Product)

Click For Summary
SUMMARY

The discussion focuses on proving the derivative of the dot product of two differentiable 3-space vector-valued functions, r1(t) and r2(t). The established formula is d/dt (r1(t) • r2(t)) = r′1(t) • r2(t) + r1(t) • r′2(t). Participants emphasize using the component form of the dot product and applying the product rule for differentiation. The key takeaway is that differentiating each component and summing the results leads to the correct proof.

PREREQUISITES
  • Understanding of vector-valued functions
  • Knowledge of the dot product definition
  • Familiarity with differentiation rules, specifically the product rule
  • Ability to manipulate scalar and vector components
NEXT STEPS
  • Study the properties of vector-valued functions in calculus
  • Learn how to apply the product rule in vector calculus
  • Explore examples of differentiating dot products of vector functions
  • Review the implications of scalar-valued functions derived from vector operations
USEFUL FOR

Students studying calculus, particularly those focusing on vector calculus, as well as educators and tutors seeking to clarify the differentiation of vector-valued functions.

karens
Messages
7
Reaction score
0

Homework Statement


n.

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

Directly from the definition of dot product, and the definition of derivative of vector-
valued functions in terms of components, prove that
d/dt (r1(t) • r2(t)) = r′1(t) • r2(t) + r1(t) • r′2(t).

Homework Equations



Dot Product: U • V = u1v1 + u2v2 + u3v3

The Attempt at a Solution



I can just substitute things forever and get nowhere...
 
Physics news on Phys.org
show us how?

in this example the dot product is a scalar valued function of t, use the component form you have shown & the product rule and it should follow straight forward
 
Last edited:
karens said:

Homework Statement


n.

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

Directly from the definition of dot product, and the definition of derivative of vector-
valued functions in terms of components, prove that
d/dt (r1(t) • r2(t)) = r′1(t) • r2(t) + r1(t) • r′2(t).

Homework Equations



Dot Product: U • V = u1v1 + u2v2 + u3v3

The Attempt at a Solution



I can just substitute things forever and get nowhere...
But have you differentiated?

Since, as you write, U• V= u1v1+ u2v2+ u3v3, (U• V)'= u1'v1+ u1v1'+ u2'v2+ u2v2'+ u3'v3+ u3v3'= (u1'v1+ u2'v2+ u3'v3)+ (u1v1'+ u2v2'+ u3v3').
 

Similar threads

Replies
6
Views
1K
Replies
1
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 2 ·
Replies
2
Views
4K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 7 ·
Replies
7
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 2 ·
Replies
2
Views
4K