Applying the Product Rule to Vector Dot Products

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SUMMARY

The discussion focuses on applying the product rule to vector dot products, specifically demonstrating that \( R \cdot \frac{dR}{dt} = 0 \) implies \( \frac{1}{2} \frac{d}{dt}[R \cdot R] = 0 \). The user initially confuses the product rule with the chain rule but is corrected that the product rule is indeed applicable to vector functions. The key takeaway is to apply the product rule correctly to derive the relationship between the dot product and its time derivative.

PREREQUISITES
  • Understanding of vector calculus
  • Familiarity with the product rule for derivatives
  • Knowledge of vector dot products
  • Basic principles of differentiation with respect to time
NEXT STEPS
  • Study the product rule for vector functions in detail
  • Practice applying the product rule to various vector calculus problems
  • Explore the implications of vector derivatives in physics
  • Review examples of dot products in motion analysis
USEFUL FOR

Students and professionals in mathematics, physics, and engineering who are working with vector calculus and need to understand the application of the product rule to vector dot products.

MeMoses
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Homework Statement


I have vector R. I need to show the R dot dR/dt = 0 => 1/2 d/dt[R dot R]


Homework Equations





The Attempt at a Solution


I guess I've never really applied the chain rule to dot products and its throwing me off. How does one go from R.dR/dt=0 to 1/2 d/dt[R.R] = 0. I have no idea to be honest. I'm not sure which direction to take it, all I know is it uses the chain rule. Sorry I haven't done much with this. I hope you can help. Thanks
 
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MeMoses said:

Homework Statement


I have vector R. I need to show the R dot dR/dt = 0 => 1/2 d/dt[R dot R]


Homework Equations





The Attempt at a Solution


I guess I've never really applied the chain rule to dot products and its throwing me off. How does one go from R.dR/dt=0 to 1/2 d/dt[R.R] = 0. I have no idea to be honest. I'm not sure which direction to take it, all I know is it uses the chain rule. Sorry I haven't done much with this. I hope you can help. Thanks

Actually it uses the product rule, which applies to vector dot products too. See: http://en.wikipedia.org/wiki/Product_rule#For_vector_functions

Try applying that on the second part, i.e. what is d/dt (R.R)?
 

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