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3 years ago

I need the answer for this

Mathematics

1 answer:

Svetach [21]3 years ago

6 0

Answer:

535.9 ft²

Step-by-step explanation:

Since there are 360° in a circle, and 240° is 2/3 of 360°, we can say that the area of the bolded sector is <em>2/3 the area of the whole circle</em>. The area of a circle with a radius of r is πr², or approximately 3.14r², so the area of the whole circle is ≈ 3.14(16)² = 3.14(256) = 803.84 ft². Taking 2/3 of this gets us 803.84 * (2/3) ≈ 535.9 ft²

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How many different ways can an after school club of 13 students line up?

maksim [4K]

Answer:

13! or 6227020800

Step-by-step explanation:

With no restrictions, we can figure out the answer to be 13! by the following analysis:

For the first position in line, there are 13 different students who could fill that spot. If we fill it and proceed to the next position in line, there are now only 12 students left who can fill it, since one is already in line. Then the next position only has 11 possibilities, and the next 10, and so on.

Multiplying all of this together gives us 13*12*11*10*9*8*7*6*5*4*3*2*1 or 13!

3 0

3 years ago

Read 2 more answers

Help pls i really need help

Naddik [55]

<h3>Answer: 33%</h3>

===========================================================

Explanation:

1/3 converts to the decimal form 0.333333... where the 3's go on forever

5/3 is a similar story but 5/3 = 1.666666.... where the '6's go on forever

The notation $0.\overline{6}$ indicates that the 6's go on forever.

So, $0.\overline{6} = 0.666666\ldots$

The horizontal bar tells us which digits repeat. As another example, $0.\overline{123} = 0.123123123123\ldots$

The three dots just mean "keep this pattern going forever".

----------

Everything mentioned so far has the decimal portions go on forever repeating some pattern over and over.

The only one that doesn't do this is 33% which converts to the decimal form 0.33

The value 0.33 is considered a terminating decimal since "terminate" means "stop". So this is the value that doesn't fit in with the other three items mentioned.

3 0

2 years ago

What is the perimeter of the rectangle in the coordinate plane?

snow_lady [41]

26 units is the answers for this questions. To find the perimeter, put a slash in each square. The only squares that will get 2 slashes is the corners

3 0

3 years ago

Read 2 more answers

The lifetime X (in hundreds of hours) of a certain type of vacuum tube has a Weibull distribution with parameters α = 2 and β =

stich3 [128]

I'm assuming $\alpha$ is the shape parameter and $\beta$ is the scale parameter. Then the PDF is

$f_X(x)=\begin{cases}\dfrac29xe^{-x^2/9}&\text{for }x\ge0\\\\0&\text{otherwise}\end{cases}$

a. The expectation is

$E[X]=\displaystyle\int_{-\infty}^\infty xf_X(x)\,\mathrm dx=\frac29\int_0^\infty x^2e^{-x^2/9}\,\mathrm dx$

To compute this integral, recall the definition of the Gamma function,

$\Gamma(x)=\displaystyle\int_0^\infty t^{x-1}e^{-t}\,\mathrm dt$

For this particular integral, first integrate by parts, taking

$u=x\implies\mathrm du=\mathrm dx$

$\mathrm dv=xe^{-x^2/9}\,\mathrm dx\implies v=-\dfrac92e^{-x^2/9}$

$E[X]=\displaystyle-xe^{-x^2/9}\bigg|_0^\infty+\int_0^\infty e^{-x^2/9}\,\mathrm x$

$E[X]=\displaystyle\int_0^\infty e^{-x^2/9}\,\mathrm dx$

Substitute $x=3y^{1/2}$ , so that $\mathrm dx=\dfrac32y^{-1/2}\,\mathrm dy$ :

$E[X]=\displaystyle\frac32\int_0^\infty y^{-1/2}e^{-y}\,\mathrm dy$

$\boxed{E[X]=\dfrac32\Gamma\left(\dfrac12\right)=\dfrac{3\sqrt\pi}2\approx2.659}$

The variance is

$\mathrm{Var}[X]=E[(X-E[X])^2]=E[X^2-2XE[X]+E[X]^2]=E[X^2]-E[X]^2$

The second moment is

$E[X^2]=\displaystyle\int_{-\infty}^\infty x^2f_X(x)\,\mathrm dx=\frac29\int_0^\infty x^3e^{-x^2/9}\,\mathrm dx$

Integrate by parts, taking

$u=x^2\implies\mathrm du=2x\,\mathrm dx$

$\mathrm dv=xe^{-x^2/9}\,\mathrm dx\implies v=-\dfrac92e^{-x^2/9}$

$E[X^2]=\displaystyle-x^2e^{-x^2/9}\bigg|_0^\infty+2\int_0^\infty xe^{-x^2/9}\,\mathrm dx$

$E[X^2]=\displaystyle2\int_0^\infty xe^{-x^2/9}\,\mathrm dx$

Substitute $x=3y^{1/2}$ again to get

$E[X^2]=\displaystyle9\int_0^\infty e^{-y}\,\mathrm dy=9$

Then the variance is

$\mathrm{Var}[X]=9-E[X]^2$

$\boxed{\mathrm{Var}[X]=9-\dfrac94\pi\approx1.931}$

b. The probability that $X\le3$ is

$P(X\le 3)=\displaystyle\int_{-\infty}^3f_X(x)\,\mathrm dx=\frac29\int_0^3xe^{-x^2/9}\,\mathrm dx$

which can be handled with the same substitution used in part (a). We get

$\boxed{P(X\le 3)=\dfrac{e-1}e\approx0.632}$

c. Same procedure as in (b). We have

$P(1\le X\le3)=P(X\le3)-P(X\le1)$

and

$P(X\le1)=\displaystyle\int_{-\infty}^1f_X(x)\,\mathrm dx=\frac29\int_0^1xe^{-x^2/9}\,\mathrm dx=\frac{e^{1/9}-1}{e^{1/9}}$

Then

$\boxed{P(1\le X\le3)=\dfrac{e^{8/9}-1}e\approx0.527}$

7 0

3 years ago

Given that the value of x is between 0 and 360 degrees (0 and 360

Brums [2.3K]

Answer:

150° and 210°
0

Step-by-step explanation:

It is convenient to memorize the trig functions of the "special angles" of 30°, 45°, 60°, as well as the way the signs of trig functions change in the different quadrants. Realizing that the (x, y) coordinates on the unit circle correspond to (cos(θ), sin(θ)) can make it somewhat easier.

You have memorized that cos(x) = (√3)/2 is true for x = 30°. That is the reference angle for the 2nd-quadrant angle 180° -30° = 150°, and for the 3rd-quadrant angle 180° +30° = 210°.

Cos(x) is negative in the 2nd and 3rd quadrants, so the angles you're looking for are

150° and 210°

<h3>Bonus</h3>

You have memorized that sin(π/4) = √2/2, and that cos(3π/4) = -√2/2. The sum of these values is ...

√2/2 + (-√2/2) = 0

_____

<em>Additional comments</em>

Your calculator can help you with both of these problems.

The coordinates given on the attached unit circle chart are (cos(θ), sin(θ)).

6 0

2 years ago