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title: 'Math 181 Miniproject 2: Population and Dosage'

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Math 181 Miniproject 2: Population and Dosage.md
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Math 181 Miniproject 2: Population and Dosage
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**Overview:**  In this miniproject you will use technological tools to turn data and into models of real-world quantitative phenomena, then apply the principles of the derivative to them to extract information about how the quantitative relationship changes.

**Prerequisites:** Sections 1.1--1.6 in *Active Calculus*, specifically the concept of the derivative and how to construct estimates of the derivative using forward, backward and central differences. Also basic knowledge of how to use Desmos. 

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1\. A settlement starts out with a population of 1000. Each year the population increases by $10\%$. Let $P(t)$ be the function that gives the population in the settlement after $t$ years.
(a) Find the missing values in the table below.
:::

(a)
| $t$    | 0    | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
|--------|------|---|---|---|---|---|---|---|
| $P(t)$ | 1000 | 1100      | 1210  | 1331  | 1464 	|  1610.51	| 1771.56 	| 1948.72





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(b) Find a formula for $P(t)$. You can reason it out directly or you can have Desmos find it for you by creating the table of values above (using $x_1$ and $y_1$ as the column labels) and noting that the exponential growth of the data should be modeled using an exponential model of the form
\\[
y_1\sim a\cdot b^{x_1}+c
\\]
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(b)
$y_1\sim a\cdot b^{x_1}+c$
a= 908.405
b= 1.10005
c= .717479

$P(t)\sim 908.405\cdot 1.10005^{x_1}+.717479$



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(c\) What will the population be after 100 years under this model?
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(c\)

$P(100)= 142944.932856$



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(d) Use a central difference to estimate the values of $P'(t)$ in the table below. What is the interpretation of the value $P'(5)$?
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(d)
Used the central difference equation of $f(a)-f(b)/a-b$
| $t$     | 1 | 2 | 3 | 4 | 5 | 6 |
|---      |---|---|---|---|---|---|
| $P'(t)$ |  105 |115.5   | 127  | 139.755  |153.78   | 169.105  |




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(e) Use a central difference to estimate the values of $P''(3)$. What is the interpretation of this value?
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(e)
12.1375 can mean the rate in which the population of the people increases per year per year

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(f) **Cool Fact:** There is a constant $k$ such that $P'(t)=k\cdot P(t)$. In other words, $P$ and $P'$ are multiples of each other.

What is the value of $k$? (You could try creating a slider and playing with the graphs or you can try an algebraic approach.)
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(f)
$k=\frac{p'\left(1\right)}{p\left(t\right)}$ 

$p'(1)+k* p(1)$
$p'(1)=k* p(1)$

$k=\frac{105}{115.5}$ 

$k=.909$


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2\. The dosage recommendations for a certain drug are based on weight.
| Weight (lbs)| 20 | 40 | 60 | 80  | 100 | 120 | 140 | 160 | 180 |
|---          |--- |--- |--- |---  |---  |---  |---  |---  |--- |
| Dosage (mg) | 10 | 30 | 70 | 130 | 210 | 310 | 430 | 570 | 730 |
(a) Find a function D(x) that approximates the dosage when you input the weight of the individual. (Make a table in Desmos using $x_1$ and $y_1$ as the column labels and you will see that the points seem to form a parabola. Use Desmos to find a model of the form
\\[
y_1\sim ax_1^2+bx_1+c
\\]
and define $D(x)=ax^2+bx+c$.)
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(a)
$y_1\sim ax_1^2+bx_1+c$
a= .025
b= -.5
c= 10

$D(x) \sim .025x^2+-.5x+10$




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(b) Find the proper dosage for a 128 lb individual.
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(b)
$D(x) \sim .025x^2+-.5x+10$
D(128) = 355.6




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(c\) What is the interpretation of the value $D'(128)$. 
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(c\)
The interpretation of D'(128) is at a weight of 128 youd need a dosage of 355.6 mg

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(d) Estimate the value of $D'(128)$ using viable techniques from our calculus class. Be sure to explain how you came up with your estimate.
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(d)
$D(x) \sim .025x^2+-.5x+10$
lim h=0, $f(128+h)-f(128)/h$
$(.025(128+h)^2 -.5(128+h)+10)-(.025(128)^2-.5(128)-10)/h$
5.75 mg/lb



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(e) Given the value $D'(130)=6$, find an equation of the tangent line to the curve $y=D(x)$ at the point where $x=130$ lbs. 
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(e)
f(a)+f'(a)(x-a)
f(130)+f'(130)(x-130)
x= 130, y= 367.5
![](https://i.imgur.com/9pyKqj2.png)



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(f) Find the point on the tangent line in the previous part that has $x$-coordinate $x=128$. Does the output value on the tangent line for $x=128$ lbs give a good estimate for the dosage for a 128 lb individual? 
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(f)
x= 128 then y or the dosage is 355.5 milligrams



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