00:01
The bac is given by this formula.
00:06
To find how quickly the bac is increasing after 10 minutes, we need to find the derivative of c.
00:14
This tells us the rate of change of c.
00:17
I'm sorry, i left out a factor of t here.
00:25
This is 0 .02 t.
00:29
Now when we calculate the derivative, we'll use the product rule.
00:32
We have 0 .02 t times negative 0 .05 e to the negative 0 .05 t power, plus 0 .02 e to the negative 0 .05 t.
00:49
We can factor out 0 .02 e to the negative 0 .05 t, and we're left with negative 0 .05 t plus 1.
01:04
To find how quickly the bac is increasing after 10 minutes, we just plug in t equals 10.
01:17
We have 0 .02 e to the negative 0 .05 times 10 times negative 0 .05 times 10 plus 1.
01:33
This is 0 .02 e to the negative 0 .5 times negative 0 .5 plus 1, which is positive 0 .5, which simplifies to 0 .01 times e to the negative 0 .5.
01:54
This calculates to approximately 0 .00607, which is 6 .07 times 10 to the negative 3.
02:14
The units are milligrams per milliliter per minute.
02:23
This is the rate of increase of the bac after 10 minutes.
02:28
The bac is maximum when the derivative is 0.
02:39
Let's see when this is.
02:41
We have 0 equals 0 .02 times e to the negative 0 .05 t multiplied by negative 0 .05 t plus 1.
03:03
I can divide out these factors here.
03:08
I'm left with 0 equals negative 0 .05 t plus 1.
03:14
We have 0 .05 t equals 1, so t equals 20.
03:24
To determine if at this time bac is maximized rather than minimized, i'm going to do the second derivative test.
03:32
C double prime is equal to, we're using the product rule, so we get the derivative of negative 0 .05 t plus 1 is just negative 0 .05...