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2 years ago

Alec is trying to find the surface area of a shoe box. What unit will he use?

1 answer:

3 0

D) Square inches.
"Square" is used when measuring area and inches are more suited for measurement due to the size of the box.

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Which pair of triangles is similar?

irina [24]

I believe the answer is the fourth option....because 13 × 3 is 39 5 × 3 is 15 and 12 × 3 is 36

6 0

2 years ago

Read 2 more answers

Solve using Fourier series.

Olin [163]

With $2L=\pi$ , the Fourier series expansion of $f(x)$ is

$\displaystyle f(x)\sim\frac{a_0}2+\sum_{n\ge1}a_n\cos\dfrac{n\pi x}L+\sum_{n\ge1}b_n\sin\dfrac{n\pi x}L$
$\displaystyle f(x)\sim\frac{a_0}2+\sum_{n\ge1}a_n\cos2nx+\sum_{n\ge1}b_n\sin2nx$

where the coefficients are obtained by computing

$\displaystyle a_0=\frac1L\int_0^{2L}f(x)\,\mathrm dx$
$\displaystyle a_0=\frac2\pi\int_0^\pi f(x)\,\mathrm dx$

$\displaystyle a_n=\frac1L\int_0^{2L}f(x)\cos\dfrac{n\pi x}L\,\mathrm dx$
$\displaystyle a_n=\frac2\pi\int_0^\pi f(x)\cos2nx\,\mathrm dx$

$\displaystyle b_n=\frac1L\int_0^{2L}f(x)\sin\dfrac{n\pi x}L\,\mathrm dx$
$\displaystyle b_n=\frac2\pi\int_0^\pi f(x)\sin2nx\,\mathrm dx$

You should end up with

$a_0=0$
$a_n=0$
(both due to the fact that $f(x)$ is odd)
$b_n=\dfrac1{3n}\left(2-\cos\dfrac{2n\pi}3-\cos\dfrac{4n\pi}3\right)$

Now the problem is that this expansion does not match the given one. As a matter of fact, since $f(x)$ is odd, there is no cosine series. So I'm starting to think this question is missing some initial details.

One possibility is that you're actually supposed to use the even extension of $f(x)$ , which is to say we're actually considering the function

$\varphi(x)=\begin{cases}\frac\pi3&\text{for }|x|\le\frac\pi3\\0&\text{for }\frac\pi3$

and enforcing a period of $2L=2\pi$ . Now, you should find that

$\varphi(x)\sim\dfrac2{\sqrt3}\left(\cos x-\dfrac{\cos5x}5+\dfrac{\cos7x}7-\dfrac{\cos11x}{11}+\cdots\right)$

The value of the sum can then be verified by choosing $x=0$ , which gives

$\varphi(0)=\dfrac\pi3=\dfrac2{\sqrt3}\left(1-\dfrac15+\dfrac17-\dfrac1{11}+\cdots\right)$
$\implies\dfrac\pi{2\sqrt3}=1-\dfrac15+\dfrac17-\dfrac1{11}+\cdots$

as required.

5 0

2 years ago

How much money would need to be deposited into an account earning 5.75% interest compounded annually in order for the accumulate

Leona [35]

I will assume you are using compound interest.

let the amount invested be x 

x(1.0575)^25 = 85000 
x = 85000/1.0575^25 = $21,009.20

6 0

2 years ago

Read 2 more answers

1. The equation y=x^2-9x+20 models the roller coasters path over time. The variable y represents height (in feet) above or below

azamat

Answer:

1) the factored form is y= ( x-5 ) ( x+4 )

2) the vertex is (4.5, -0.25)

3) the y intercept is when x equals 0 so it is at (0,20)

4) it opens upward and the vertex is (4.5, -0.25) the x intercepts are (4,0) and (5,0) and the y intercept is (0,20)

a. it dips between 4 seconds and 5 seconds so the x intercepts are (4,0) and (5,0)

b. it is taken at the vertex aka the lowest point so the height is -0.25

8 0

3 years ago

Read 2 more answers

(-4,r) (-8,3) m=5 Find r please!

viva [34]

Answer:

r = 23

Step-by-step explanation:

m = (y2 - y1)/(x2 - x1)

5 = (3 - r)/(-8 - (-4))

5 = (3 - r)/(-8 + 4)

3 - r = 5 × -4

3 - r = -20

-r = -23

r = 23

4 0

2 years ago