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Sindrei [870]
3 years ago
14

A. Evaluate ∫20 tan 2x sec^2 2x dx using the substitution u = tan 2x.

Mathematics
1 answer:
irakobra [83]3 years ago
3 0

Answer:

The integral is equal to 5\sec^2(2x)+C for an arbitrary constant C.

Step-by-step explanation:

a) If u=\tan(2x) then du=2\sec^2(2x)dx so the integral becomes \int 20\tan(2x)\sec^2(2x)dx=\int 10\tan(2x) (2\sec^2(2x))dx=\int 10udu=\frac{u^2}{2}+C=10(\int udu)=10(\frac{u^2}{2}+C)=5\tan^2(2x)+C. (the constant of integration is actually 5C, but this doesn't affect the result when taking derivatives, so we still denote it by C)

b) In this case u=\sec(2x) hence du=2\tan(2x)\sec(2x)dx. We rewrite the integral as \int 20\tan(2x)\sec^2(2x)dx=\int 10\sec(2x) (2\tan(2x)\sec(2x))dx=\int 10udu=5\frac{u^2}{2}+C=5\sec^2(2x)+C.

c) We use the trigonometric identity \tan(2x)^2+1=\sec(2x)^2 is part b). The value of the integral is 5\sec^2(2x)+C=5(\tan^2(2x)+1)+C=5\tan^2(2x)+5+C=5\tan^2(2x)+C. which coincides with part a)

Note that we just replaced 5+C by C. This is because we are asked for an indefinite integral. Each value of C defines a unique antiderivative, but we are not interested in specific values of C as this integral is the family of all antiderivatives. Part a) and b) don't coincide for specific values of C (they would if we were working with a definite integral), but they do represent the same family of functions.  

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David is filling out orders for an online business and gets paid $1 for each order he fills out plus bonus of 25 cents per order
svp [43]

Answer:

David will make $481 (he earns the bonus)

Explanation:

<em>If he makes $1 for each order and he filled out 385 orders, then why can't we say he made $385?</em>

Because of this statement rights here:

"...and gets paid $1 for each order he fills out plus bonus of 25 cents per order if the average number of orders he completes per day within any of the given weeks exceeds 20."

So we need to find out if any of the 3 weeks has an average of 20+ orders per day.

<h2>David is filling out orders for an online business and gets paid $1 for each order he fills out</h2>

(x is the amount of orders he fills out)

profit = $1x

<h2>plus bonus of 25 cents per order if the average number of orders he completes per day within any of the given weeks exceeds 20. </h2>

if any average orders per day is > 20 in any week

bonus profit = $1.25x

<h2>The ratio of the number of orders he processed during the first week to the number of orders he processed during the second week is 3:2, </h2>

first week     second week

             3a : 2a

<h2>while the the ratio that compares the number of orders he filled out during the first and the third weeks is 4 to 5 respectively. </h2>

first week   third week

           4a : 5a

<h2>What amount of money will David make at the end of three weeks if the total number of orders he filled out was 385?</h2>

sum of all ratios of a = 385

So we have

3a : <u>2a</u> (first week to <u>second week</u>)

4a : <em>5a </em>(first week to <em>third week</em>)

Notice how the first two numbers are both from the first week. Let's use the Least Common Multiple to make them equal while still keeping ratios.

LCM of 3 and 4: 12 = 3 * 4

12a : <u>8a</u> ( times 4 )

12a : <em>15a</em> ( times 3 )

Now that we have the same value, we can create a big ratio

first week <u>second week</u> <em>third week</em>

   12a     :        <u>8a</u>          :      <em>15a</em>

we know that these ratios will all equal 385. Since ratios are equal no matter how big we make them, we can say that

12a + <u>8</u>a + <em>15</em>a = 385 (a is a variable to scale up the ratio)

which is the same as

(12 + <u>8</u> + <em>15</em>) * a = 385

(<em><u>35</u></em>) * a = 385

35a = 385

if we solve for a by dividing 35 on both sides we get

a = 11

This gives us how much to multiply the RATIO by to get the ACTUAL NUMBER of orders completed. Let's plug 11 for 'a' and see what happens.

12a + <u>8</u>a + <em>15</em>a = 385

12(11) + <u>8</u>(11) + <em>15</em>(11) = 385

132 + <u>88</u> + <em>165</em> = 385     (Check that out, the number of orders each week!)

<u>220</u> + <em>165</em> = 385

<em><u>385</u></em> = 385

Bingo! All the math works out. So, looking back at the verryyy top of this problem, the reason why it wasn't as easy as $385 was because of the bonus.

The bonus gives David $1.25 per order instead of $1 per order if any of the weeks have an average ORDER PER DAY of anything bigger than 20. If we know the real numbers of orders for every week (132, <u>88</u>, and <em>165</em>), then we can divide it by 7 to get the average order per day. Let's choose <em>165 </em>(the <em>third week</em>) because it is the biggest and has the greatest chance of meeting our goal.

165 orders / 7 days (7 days in a week) = 23.57 orders per day

Is this greater than 20 orders per day?

YES!

So now we can safely say that the bonus is there or not, and in this case, the bonus IS there because there is a week where David had more than 20 orders per day.

So instead of using

profit = $1x

We will use

bonus profit = $1.25x

(x is the amount of orders completed)

So if we know he completed 385 orders, and we know he earned the bonus, we plug in 385 for x for the bonus function

bonus profit = $1.25x

bonus profit = $1.25 * 385

bonus profit = $481.25

If necessary, round your answer to the nearest dollar.

So for the very end, all we have to do is round it to the nearest dollar.

$481.25 rounds to $481.

And we're done!

8 0
3 years ago
Carlos is using the distributive property to evaluate the expression 14 (49) by using friendlier numbers. His work is shown belo
Natasha2012 [34]
Separating 49 into 40+9
7 0
3 years ago
Read 2 more answers
The newborn weights 7 pounds and is 21 inches long. What is the ratio of weight to length?​
Nikolay [14]

Answer:

1:3

Step-by-step explanation:

The required ratio will be ,

7:21

= 1 :3

4 0
3 years ago
Read 2 more answers
Tim installs 50 square feet on his floor in 45 minutes. At this rate, how long does it take him to install 495 square feet?
Katena32 [7]

Answer:

445.5 minutes

or 7 hours 25 minutes 30 seconds

Step-by-step explanation:

We can use ratio's to solve

50 ft^2           495 ft^2

--------------  = ------------

45 minutes    x minutes

Using cross products

50x = 45*495

50x=22275

Divide each side by 50

50x/50 = 22275/50

x =445.5

445.5 minutes

If we want to convert to hours and minutes, divide by 60

7 hours is 420 minutes

445.5 -420 = 25.5

7 hours 25 minutes

.5 minutes is 30 seconds

7 hours 25 minutes 30 seconds

6 0
2 years ago
The length of fencing required for a rectangular garden in terms of its width, x, if it’s length is 2 units more than 1.5 times
JulijaS [17]

Answer:

5x+4 units.

Step-by-step explanation:

Let x be the width of rectangle.

We have been given that the length of garden is 2 units more than 1.5 times it’s width. So length of the rectangle will be: 1.5x+2.

To find the length of total fencing we need to figure out perimeter of rectangle with width x and length 1.5x+2.

Since we know that perimeter of a rectangle is two times the sum of its length and width.

\text{Perimeter of rectangle}=2(\text{Length+Width})

Upon substituting length and width of garden in above formula we will get,

\text{Perimeter of rectangular garden}=2(1.5x+2+x)

\text{Perimeter of rectangular garden}=2(2.5x+2)

Upon using distributive property we will get,

\text{Perimeter of rectangular garden}=2*2.5x+2*2

\text{Perimeter of rectangular garden}=5x+4

Therefore, the length of required fencing will be 5x+4 units.

4 0
3 years ago
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