
Review!
Calculus is the mathematics of change, and everything changes with respect to time.
In algebra we study the relationship between variables.
In calculus we study the relationship between the rate of change of variables.
There are infinite amount of scenarios that can be produced.
- A bathtub is filling at the rate of 2gal/min
- A balloon is deflating at a rate of 3 cubic centimeters/second
- A football is kicked with an initial upward velocity of 30yd/s
Lets translate these scenarios into mathematical models!
all theses scenarios are rates volume changing respect to time.
Now let's play with some real related rates problems!
Make sure you have the exploration in front of you!
Rippling Water Problem
- This problem deals with the radius of the circle, and the area.
Therefore we should write out the equation involving two different variables.
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Let A be Area
Now we are using Implicit Differentiation
to express the rate of change of the area of the circle with respect to time t.
Process starts with stating that this equation will be derived with respect to variable.
Use chain rule to implicitly differentiate the equation.
This is the hardest part where everyone is having hard time, or at least some of us!!
It is simple, let's look at again.
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- This is our original equation
each of variables, in this case A and r, is a function composed with t.
Since the letter r itself is a function, outside function is squared, and inside function is r
Using chain rule,
derive the outside, leave inside alone
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- We get the result.
now we have to multiply the derivative of inside function, which is r'
However, since the function r is the function of t, we can also write out the derivative of r in different form.
It's the change in numerator over change in denominator.
This is why there is additional fraction representing derivative after each implicit differentiations.
This is how to do the implicit differentiation relating two different rates.
Rest of the question and answers are posted in Bru's post of Friday's class.
If there is any additional question, please let me know.
-Hyunhwa-
:0 Our next Scribe Post will be by Skirdude