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3 years ago

Cos15°°- Sin 15°= 1/√2

Mathematics

1 answer:

ololo11 [35]3 years ago

4 0

<h2>Refer this attachment</h2>

Hope it's help you

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Which of the following rational numbers is equal to 4 point 5 with bar over 5?

steposvetlana [31]

41/9 = 4.5 with a bar over 5 because it is repeating

5 0

3 years ago

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The four angles of a quadrilateral are in the ratio 2:3:5:8. Find the angles

sp2606 [1]

Answer:

Step-by-step explanation: let 2:3:5:8 be 2x,3x,5x,8x respectively .

*angles in a quadrilateral is 360 degree

*2x+3x+5x+8x=360

*18x=360

*x=360/18

*x=20

now substitute x in these:

2x=2x20=40

3x=3x20=60

5x=5x20=100

8x=8x20= 160

so these are the following angles: 40,60,100 and 160

8 0

3 years ago

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

PLEASE HELP!!

olga_2 [115]

The value of a = 2.17 and b = 1.95.

<h3>What is regression line?</h3>

A regression line is a graphic representation of the regression equation expressing the hypothesized relationship between an outcome or dependent variable and one or more predictors or independent variables;

y= $2.01*1.93^{x}$

Correlation:

r=0.964

R-squared:

r²=0.9292

Hence, value of a and b is 2.17 and 1.95.

learn more about regression line here:

brainly.com/question/11340674

#SPJ1

8 0

2 years ago

Pls can someone help me. I m giving 10 pts . I may mark you as the braniliest

worty [1.4K]

100 notes were altogether

Solution:

Given that ratio of the number of $2 notes to the number of $5 notes was 4 : 1

number of $2 notes : number of $5 notes = 4 : 1

Let 4x be the number of $ 2 notes

Let 1x be the number of $ 5 notes

Given that total value of notes is $ 260

Therefore,

$ 2 (number of $ 2 notes ) + $ 5(number of $ 5 notes ) = $ 260

$ 2(4x) + $ 5(1x) = $ 260

8x + 5x = 260

13x = 260

x = 20

Thus number of notes altogether is given as:

4x + 1x = 4(20) + 1(20) = 80 + 20 = 100

Thus 100 notes were altogether

4 0

3 years ago

Cos15°°- Sin 15°= 1/√2​

Cos15°°- Sin 15°= 1/√2