Help with Vector Calculus Derivative

In summary, The conversation discusses the use of the dot product in taking the derivative of a vector function. One person is confused about how to get the result of 2r'(t) dot r(t) and the other person suggests using the property a dot (b + c) = a dot b + a dot c. They also mention the fundamental property of the dot product a.b = b.a.
  • #1
rad0786
188
0
Hey... i was hopeing somebody can help me with a homework question... its about vector calc... taking the deriviative.

d/dx[r(t) dot r(t)] = r'(t) dot r(t) + r(t) dot r'(t) = 2r'(t) dot r(t)

I know it sounds sillly, but i was just wondering how on Earth they got
2r'(t) dot r(t) ?
 
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  • #2
Well, go through the list of properties of the dot product -- any of them look useful?
 
  • #3
Another approach... what must be true for that last equality
r'(t) dot r(t) + r(t) dot r'(t) = 2r'(t) dot r(t)
to happen (assuming that each side is correct)?
This should lead to the property hinted by Hurkyl.
 
  • #4
Okay i see it now.

It comes from the property...

a dot (b + c) = a dot b + a dot c

:)

Thanks for poinitng that out...
 
  • #5
Ah, right -- that one's so fundamental I forgot it even needed to be invoked! (I had only noticed you needed a.b = b.a)
 

1. What is a vector calculus derivative?

A vector calculus derivative is a mathematical operation that calculates the rate of change of a vector quantity with respect to another variable. It is used to analyze the behavior of vector fields and is an essential tool in fields such as physics, engineering, and economics.

2. How do you find a derivative of a vector function?

To find the derivative of a vector function, you can use the same rules as for finding the derivative of a scalar function. However, instead of using single numbers, you will use vectors in the calculations. The derivative of a vector function is a vector itself.

3. What is the difference between a scalar and vector derivative?

A scalar derivative is the derivative of a scalar function, which has one independent variable and one dependent variable. On the other hand, a vector derivative is the derivative of a vector function, which has multiple independent variables and multiple dependent variables. Scalar derivatives result in a single numerical value, while vector derivatives result in a vector quantity.

4. What are some practical applications of vector calculus derivatives?

Vector calculus derivatives have a wide range of practical applications, including analyzing fluid flow in engineering, modeling the trajectory of projectiles in physics, and optimizing production processes in economics. They are also used in computer graphics to create realistic 3D images and animations.

5. What are some tips for solving problems involving vector calculus derivatives?

Some tips for solving problems involving vector calculus derivatives include understanding the basic rules of vector calculus, carefully identifying the variables and functions involved, and practicing with different types of problems. It is also helpful to visualize the vectors and their behavior in order to better understand the problem and solution.

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