
#1
Mar912, 12:34 PM

P: 42

1. The problem statement, all variables and given/known data
My question is how do I take the time derivative of (theta dot)^2? 2. Relevant equations 3. The attempt at a solution Is the answer just 2(theta double dot)^1 or do you use chain rule 2(theta dot)*(theta double dot)? 



#2
Mar912, 12:40 PM

P: 129

Well, assuming theta is a function of time, you must use the chain rule!




#3
Mar912, 12:40 PM

Math
Emeritus
Sci Advisor
Thanks
PF Gold
P: 38,898

I take that your "dot" refers to differentiation with respect to time, t, I will use a prime since it is simpler here and you are asking about the derivative of [itex](\theta')^2[/itex].
The derivative of any [itex](f(t))^2[/itex] with respect to t is [itex]2f(t)f'(t)[/itex], by the chain rule, so the derivative of [itex](\theta(t)')^2[/itex] is [itex]2(\theta')(\theta'')[/itex]. 


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