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3 years ago

Write an equation in standard form of the circle with the given properties.

Mathematics

1 answer:

agasfer [191]3 years ago

6 0

Answer:

x² + y² = 6

Step-by-step explanation:

The standard form of the equation of a circle centred at the origin is

x² + y² = r² ( r is the radius )

Here r = $\sqrt{6}$ , then

x² + y² = ( $\sqrt{6}$ )² , that is

x² + y² = 6

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The joint probability density function of X and Y is given by fX,Y (x, y) = ( 6 7 x 2 + xy 2 if 0 < x < 1, 0 < y < 2

fredd [130]

I'm going to assume the joint density function is

$f_{X,Y}(x,y)=\begin{cases}\frac67(x^2+\frac{xy}2\right)&\text{for }0$

a. In order for $f_{X,Y}$ to be a proper probability density function, the integral over its support must be 1.

$\displaystyle\int_0^2\int_0^1\frac67\left(x^2+\frac{xy}2\right)\,\mathrm dx\,\mathrm dy=\frac67\int_0^2\left(\frac13+\frac y4\right)\,\mathrm dy=1$

b. You get the marginal density $f_X$ by integrating the joint density over all possible values of $Y$ :

$f_X(x)=\displaystyle\int_0^2f_{X,Y}(x,y)\,\mathrm dy=\boxed{\begin{cases}\frac67(2x^2+x)&\text{for }0$

c. We have

$P(X>Y)=\displaystyle\int_0^1\int_0^xf_{X,Y}(x,y)\,\mathrm dy\,\mathrm dx=\int_0^1\frac{15}{14}x^3\,\mathrm dx=\boxed{\frac{15}{56}}$

d. We have

$\displaystyle P\left(X$

and by definition of conditional probability,

$P\left(Y>\dfrac12\mid X\frac12\text{ and }X$

$\displaystyle=\dfrac{28}5\int_{1/2}^2\int_0^{1/2}f_{X,Y}(x,y)\,\mathrm dx\,\mathrm dy=\boxed{\frac{69}{80}}$

e. We can find the expectation of $X$ using the marginal distribution found earlier.

$E[X]=\displaystyle\int_0^1xf_X(x)\,\mathrm dx=\frac67\int_0^1(2x^2+x)\,\mathrm dx=\boxed{\frac57}$

f. This part is cut off, but if you're supposed to find the expectation of $Y$ , there are several ways to do so.

Compute the marginal density of $Y$ , then directly compute the expected value.

$f_Y(y)=\displaystyle\int_0^1f_{X,Y}(x,y)\,\mathrm dx=\begin{cases}\frac1{14}(4+3y)&\text{for }0$

$\implies E[Y]=\displaystyle\int_0^2yf_Y(y)\,\mathrm dy=\frac87$

Compute the conditional density of $Y$ given $X=x$ , then use the law of total expectation.

$f_{Y\mid X}(y\mid x)=\dfrac{f_{X,Y}(x,y)}{f_X(x)}=\begin{cases}\frac{2x+y}{4x+2}&\text{for }0$

The law of total expectation says

$E[Y]=E[E[Y\mid X]]$

We have

$E[Y\mid X=x]=\displaystyle\int_0^2yf_{Y\mid X}(y\mid x)\,\mathrm dy=\frac{6x+4}{6x+3}=1+\frac1{6x+3}$

$\implies E[Y\mid X]=1+\dfrac1{6X+3}$

This random variable is undefined only when $X=-\frac12$ which is outside the support of $f_X$ , so we have

$E[Y]=E\left[1+\dfrac1{6X+3}\right]=\displaystyle\int_0^1\left(1+\frac1{6x+3}\right)f_X(x)\,\mathrm dx=\frac87$

5 0

3 years ago

How do you solve 54=-9d

kiruha [24]

Hey there!

To solve this, divide the numbers 54 and -9 . . .

54 divided by -9 = -6 <------------

(-6) x -9 = 54

_________________
d = -6

_________________

Hope this helps you.
Have a great day!

7 0

3 years ago

Read 2 more answers

Consider w=sqrrt2/2(cos(225°) + isin(225°)) and z = 1(cos(60°) + isin(60°)). What is w+ z expressed in rectangular form?

SVETLANKA909090 [29]

Answer:

Option (3)

Step-by-step explanation:

w = $\frac{\sqrt{2}}{2}[\text{cos}(225) + i\text{sin}(225)]$

Since, cos(225) = cos(180 + 45)

= -cos(45) [Since, cos(180 + θ) = -cosθ]

= - $\frac{\sqrt{2}}{2}$

sin(225) = sin(180 + 45)

= -sin(45)

= - $\frac{\sqrt{2}}{2}$

Therefore, w = $\frac{\sqrt{2}}{2}[-\frac{\sqrt{2}}{2}+i(-\frac{\sqrt{2}}{2})]$

= $-\frac{2}{4}(1+i)$

= $-\frac{1}{2}(1+i)$

z = 1[cos(60) + i(sin(60)]

= $[\frac{1}{2}+i(\frac{\sqrt{3}}{2})$

= $\frac{1}{2}(1+i\sqrt{3})$

Now (w + z) = $-\frac{1}{2}(1+i)+\frac{1}{2}(1+i\sqrt{3})$

= $-\frac{1}{2}-\frac{i}{2}+\frac{1}{2}+i\frac{\sqrt{3}}{2}$

= $\frac{(i\sqrt{3}-i)}{2}$

= $\frac{(\sqrt{3}-1)i}{2}$

Therefore, Option (3) will be the correct option.

3 0

3 years ago

Read 2 more answers

Can someone please help me with this???

8_murik_8 [283]

there would be 38 woman

8 0

4 years ago

Evaluate the expression 3.14(a2 + ab) when a = 3 and b = 4.

Lady_Fox [76]

Hey there!

3.14(a^2 + ab)

= 3.14(3^2 + 3 *4)

3^2

= 3 * 3

= 9

3 * 4

= 12

3.14(9 + 12)

9 + 12

= 21

3.14(21)

= 65.94

Answer: 65.94

Good luck on your assignment and enjoy your day!

~Amphitrite1040:)

6 0

3 years ago

Read 2 more answers