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3 years ago

Please help me I’m struggling

Mathematics

1 answer:

ryzh [129]3 years ago

4 0

Answer:

Step-by-step explanation:

Remark

This is a cosine law problem.

a = 12

b = 15

C = 83

Notice that the angle is enclosed by 2 given sides. That's what a cosine problem looks like (one of the two choices.

Formula

c^2 = a^2 + b^2 - 2ab*cos(C)

Solution

c^2 = 12^2 + 15^2 - 2*12*15 * cos(83)

c^2 = 144 + 225 - 360 * cos(83)

cos(83) = 0.1219

c^2 = 144 + 225 - 360 * 0.1219

c^2 = 369 - 43.884

c^2 = 325.116

sqrt(c^2) = sqrt(325.116)

c = 18.031

To the nearest tenth, the answer is 18.0 and you must include the 0.

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99 POINT QUESTION, PLUS BRAINLIEST!!!

VladimirAG [237]

First, we have to convert our function (of x) into a function of y (we revolve the curve around the y-axis). So:

$y=100-x^2\\\\x^2=100-y\qquad\bold{(1)}\\\\\boxed{x=\sqrt{100-y}}\qquad\bold{(2)} \\\\\\0\leq x\leq10\\\\y=100-0^2=100\qquad\wedge\qquad y=100-10^2=100-100=0\\\\\boxed{0\leq y\leq100}$

And the derivative of x:

$x'=\left(\sqrt{100-y}\right)'=\Big((100-y)^\frac{1}{2}\Big)'=\dfrac{1}{2}(100-y)^{-\frac{1}{2}}\cdot(100-y)'=\\\\\\=\dfrac{1}{2\sqrt{100-y}}\cdot(-1)=\boxed{-\dfrac{1}{2\sqrt{100-y}}}\qquad\bold{(3)}$

Now, we can calculate the area of the surface:

$A=2\pi\int\limits_0^{100}\sqrt{100-y}\sqrt{1+\left(-\dfrac{1}{2\sqrt{100-y}}\right)^2}\,\,dy=\\\\\\= 2\pi\int\limits_0^{100}\sqrt{100-y}\sqrt{1+\dfrac{1}{4(100-y)}}\,\,dy=(\star)$

We could calculate this integral (not very hard, but long), or use (1), (2) and (3) to get:

$(\star)=2\pi\int\limits_0^{100}1\cdot\sqrt{100-y}\sqrt{1+\dfrac{1}{4(100-y)}}\,\,dy=\left|\begin{array}{c}1=\dfrac{-2\sqrt{100-y}}{-2\sqrt{100-y}}\end{array}\right|= \\\\\\= 2\pi\int\limits_0^{100}\dfrac{-2\sqrt{100-y}}{-2\sqrt{100-y}}\cdot\sqrt{100-y}\cdot\sqrt{1+\dfrac{1}{4(100-y)}}\,\,dy=\\\\\\ 2\pi\int\limits_0^{100}-2\sqrt{100-y}\cdot\sqrt{100-y}\cdot\sqrt{1+\dfrac{1}{4(100-y)}}\cdot\dfrac{dy}{-2\sqrt{100-y}}=\\\\\\$

$=2\pi\int\limits_0^{100}-2\big(100-y\big)\cdot\sqrt{1+\dfrac{1}{4(100-y)}}\cdot\left(-\dfrac{1}{2\sqrt{100-y}}\, dy\right)\stackrel{\bold{(1)}\bold{(2)}\bold{(3)}}{=}\\\\\\= \left|\begin{array}{c}x=\sqrt{100-y}\\\\x^2=100-y\\\\dx=-\dfrac{1}{2\sqrt{100-y}}\, \,dy\\\\a=0\implies a'=\sqrt{100-0}=10\\\\b=100\implies b'=\sqrt{100-100}=0\end{array}\right|=\\\\\\= 2\pi\int\limits_{10}^0-2x^2\cdot\sqrt{1+\dfrac{1}{4x^2}}\,\,dx=(\text{swap limits})=\\\\\\$

$=2\pi\int\limits_0^{10}2x^2\cdot\sqrt{1+\dfrac{1}{4x^2}}\,\,dx= 4\pi\int\limits_0^{10}\sqrt{x^4}\cdot\sqrt{1+\dfrac{1}{4x^2}}\,\,dx=\\\\\\= 4\pi\int\limits_0^{10}\sqrt{x^4+\dfrac{x^4}{4x^2}}\,\,dx= 4\pi\int\limits_0^{10}\sqrt{x^4+\dfrac{x^2}{4}}\,\,dx=\\\\\\= 4\pi\int\limits_0^{10}\sqrt{\dfrac{x^2}{4}\left(4x^2+1\right)}\,\,dx= 4\pi\int\limits_0^{10}\dfrac{x}{2}\sqrt{4x^2+1}\,\,dx=\\\\\\=\boxed{2\pi\int\limits_0^{10}x\sqrt{4x^2+1}\,dx}$

Calculate indefinite integral:

$\int x\sqrt{4x^2+1}\,dx=\int\sqrt{4x^2+1}\cdot x\,dx=\left|\begin{array}{c}t=4x^2+1\\\\dt=8x\,dx\\\\\dfrac{dt}{8}=x\,dx\end{array}\right|=\int\sqrt{t}\cdot\dfrac{dt}{8}=\\\\\\=\dfrac{1}{8}\int t^\frac{1}{2}\,dt=\dfrac{1}{8}\cdot\dfrac{t^{\frac{1}{2}+1}}{\frac{1}{2}+1}=\dfrac{1}{8}\cdot\dfrac{t^\frac{3}{2}}{\frac{3}{2}}=\dfrac{2}{8\cdot3}\cdot t^\frac{3}{2}=\boxed{\dfrac{1}{12}\left(4x^2+1\right)^\frac{3}{2}}$

And the area:

$A=2\pi\int\limits_0^{10}x\sqrt{4x^2+1}\,dx=2\pi\cdot\dfrac{1}{12}\bigg[\left(4x^2+1\right)^\frac{3}{2}\bigg]_0^{10}=\\\\\\= \dfrac{\pi}{6}\left[\big(4\cdot10^2+1\big)^\frac{3}{2}-\big(4\cdot0^2+1\big)^\frac{3}{2}\right]=\dfrac{\pi}{6}\Big(\big401^\frac{3}{2}-1^\frac{3}{2}\Big)=\boxed{\dfrac{401^\frac{3}{2}-1}{6}\pi}$

Answer D.

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4 years ago

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The height, h, in feet of a piece of cloth tied to a waterwheel in relation to sea level as a function of time, t, in seconds ca

Anni [7]

Considering the period of the cosine function, it is found that it takes 40 seconds for the wheel to complete one turn.

<h3>What is the period of the cosine function?</h3>

The cosine function is defined by:

f(x) = acos(bx + c) + d.

For the period, we have to look at coefficient b, and the period is:

P = 2π/|B|

For this problem, the function is given by:

h(x) = 15 cos(π/20)

Hence B = π/20, and the period is:

P = 2π/|B| = 2π/(π/20) = 2 x 20 = 40 seconds.

Hence it takes 40 seconds for the wheel to complete one turn.

More can be learned about the period of trigonometric functions at brainly.com/question/12502943

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2 years ago

Find the unit rate.<br><br> 3.75 pints out of every 5 gallons

Veronika [31]

Answer:

1 pints out of every 1.2 gallons.

Step-by-step explanation:

3.75/3.75 = 1

5/3.75 = 1.33 repeating

1 pints out of every 1.2 gallons.

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3 years ago

How do you find the fist step to solving the system of equations x+y=8 and 3x-2y=-6

Whitepunk [10]

Answer:

The first stpe in solving this system of equations is finding either X or Y in terms of the other variable. Ex: x = 8 - y or y = 8 - x

Step-by-step explanation:

When faced with a system of equations problem, you need to find one variable at a time. To do this, you need to eliminate one of the variables from one of the equations. I used x + y = 8 because that was simplier to find one of the variables from. From there, you can substitute that in for the variabel in the secone equation.

3x - 2y = -6

3x - 2(8 - x) = -6

3x - 16 + 2x = -6

5x - 16 = -6

5x = 10

x = 2

Than you can use that and plug it back into one of the original equations to find the other variable.

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2 years ago

HELP!! 50 POINTS!!!

aalyn [17]

Step-by-step explanation:

We have been given a table, which represents the projected value of two different houses for three years.

Part A:

$\text{Increase in value of house 1 after one year}=294,580-286,000$

$\text{Increase in value of house 1 after one year}=8580$

$\text{Increase in value of house 1 after two years}=303,417.40-294,580$

$\text{Increase in value of house 1 after two years}=8837.4$

We can see from our given table that the value of house 1 is not increasing at a constant rate, while a linear function has a constant rate of change, therefore, an exponential function can be used to describe the value of the house 1 after a fixed number of years.

$\text{Increase in value of house 2 after one year}=295,000-286,000$

$\text{Increase in value of house 2 after one year}=9,000$

$\text{Increase in value of house 2 after two years}=304,000-295,000$

$\text{Increase in value of house 2 after two years}=9,000$

We can see from our given table that the value of house 2 is increasing at a constant rat that is $9,000 per year. Since a linear function has a constant rate of change, therefore, a linear function can be used to describe the value of the house 2 after a fixed number of years.

Part B:

Let x be the number of years after Dominique bought the house 1.

Since value of house 1 is increasing exponentially, so let us find increase percent of value of house 1.

$\text{Increase }\%=\frac{\text{Final value-Initial value}}{\text{Initial value}}\times 100$

$\text{Increase }\%=\frac{294,580-286,000}{286,000}\times 100$

$\text{Increase }\%=\frac{8580}{286,000}\times 100$

$\text{Increase }\%=0.03\times 100$

$\text{Increase }\%=3$

$\text{Increase }\%=\frac{303,417.40-294,580}{294,580}\times 100$

$\text{Increase }\%=\frac{8837.4}{294,580}\times 100$

$\text{Increase }\%=0.03\times 100$

$\text{Increase }\%=3$

Therefore, the growth rate of house 1's value is 3%.

Since we know that an exponential function is in form: $y=a*b^x$ , where,

a = Initial value,

b = For growth b is in form (1+r), where, r is rate in decimal form.

$3\%=\frac{3}{100}=0.03$

Upon substituting our values in exponential function form we will get,

$f(x)=286,000(1+0.03)^x$ , where, f(x) represents the value of the house 1, in dollars, after x years.

Therefore, the function $f(x)=286,000(1.03)^x$ represents the value of house 1 after x years.

Let x be the number of years after Dominique bought the house 2.

We can see that when Dominique bought house 2 it has a value of $286,000. This means that at x equals 0 value of house will be $286,000 and it will be our y-intercept.

Since value of house 2 is increasing 9000 per year, therefore, slope of our line be 9000.

Upon substituting these values in slope-intercept form of equation $(y=mx+b)$ we will get,

$f(x)=9000x+286,000$ , where, f(x) represents the value of the house 2, in dollars, after x years.

Therefore, the function $f(x)=9000x+286,000$ represents the value of house 2 after x years.

Part C:

Since values in exponential function increases faster than linear function, so the value of house 1 will be greater than value of house 2.

Let us find the value of house 1 and house 2 by substituting x=25 in our both functions.

$f(25)=286,000(1.03)^{25}$

$f(25)=286,000*2.0937779296542148$

$f(25)=598820.48788$

We can see that value of house 1 after 25 years will be approx $598,820.48.

$f(25)=9000*25+286,000$

$f(25)=225,000+286,000$

$f(25)=511,000$

We can see that value of house 2 after 25 years will be approx $511,000.

Since $511,000 is less than $598820.48, therefore, value of house 1 is greater than value of house 2.

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4 years ago

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