Help deriving an equation using chain rule

In summary, the conversation discusses using the chain rule to derive the equation for r" from r'. The homework equations include the definitions for distance (r), velocity (v), and acceleration (a), as well as the chain rule. The question asks for help in applying the chain rule to the specific variables involved.
  • #1
yugeci
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Homework Statement



cdd8aadb54f538338f2d5063eab8f924.png


How does one get the r" equation from r'?

Homework Equations



r = distance
v = r' = ds/dt
a = r'' = dv/dt

chain rule, dy/dt = dy/dx * dx/dt

The Attempt at a Solution



I can easily get to r' from r using the chain rule but how do you derive r" from r'? How do you apply the chain rule when there are 3 variables (sec theta, tan theta and theta dot)?

Help would be appreciated.
 
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  • #2
[itex] \frac{d}{dt} f(a(t),b(t),c(t))=\frac{\partial f}{\partial a}\dot a+\frac{\partial f}{\partial b} \dot b+\frac{\partial f}{\partial c} \dot c [/itex]
 
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1. How do I use the chain rule to derive an equation?

The chain rule is a calculus concept used to find the derivative of a composite function. To use the chain rule, you must first identify the "inside" and "outside" functions of the composite function. Then, you can use the formula d/dx(f(g(x))) = f'(g(x)) * g'(x) to derive the equation.

2. Can you provide an example of using the chain rule to derive an equation?

Sure! Let's say we have the composite function f(x) = (3x^2 + 2)^3. The "inside" function is g(x) = 3x^2 + 2 and the "outside" function is h(x) = x^3. We can use the formula d/dx(f(g(x))) = f'(g(x)) * g'(x) to find the derivative of f(x) as follows:
f'(x) = h'(g(x)) * g'(x) = (3x^2)^3 * (6x) = 54x^7

3. What are the common mistakes made when using the chain rule to derive an equation?

One common mistake is incorrectly identifying the "inside" and "outside" functions. Another mistake is not properly applying the formula d/dx(f(g(x))) = f'(g(x)) * g'(x). It is also important to remember to use the chain rule multiple times if there are multiple nested functions.

4. How can I check if my derived equation using the chain rule is correct?

You can check your derived equation by taking the derivative of the original function and comparing it to the derivative you found using the chain rule. If they are the same, then your derived equation is correct.

5. Can the chain rule be used to derive equations with more than two nested functions?

Yes, the chain rule can be used for any number of nested functions. You would simply continue applying the formula d/dx(f(g(x))) = f'(g(x)) * g'(x) for each nested function until you reach the outermost function.

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