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3 years ago

Does anyone get this? The answers are A - 22.8 B - 25.5 C - 14.1 D - 31.2

Mathematics

2 answers:

Sedbober [7]3 years ago

6 0

Yeah i think you are suppose to add

Rom4ik [11]3 years ago

5 0

Answer:

Step-by-step explanation:

I think your supposed to add all those numbers together

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4. Using the geometric sum formulas, evaluate each of the following sums and express your answer in Cartesian form.

nikitadnepr [17]

Answer:

$\sum_{n=0}^9cos(\frac{\pi n}{2})=1$

$\sum_{k=0}^{N-1}e^{\frac{i2\pi kk}{2}}=0$

$\sum_{n=0}^\infty (\frac{1}{2})^n cos(\frac{\pi n}{2})=\frac{1}{2}$

Step-by-step explanation:

$\sum_{n=0}^9cos(\frac{\pi n}{2})=\frac{1}{2}(\sum_{n=0}^9 (e^{\frac{i\pi n}{2}}+ e^{\frac{i\pi n}{2}}))$

$=\frac{1}{2}(\frac{1-e^{\frac{10i\pi}{2}}}{1-e^{\frac{i\pi}{2}}}+\frac{1-e^{-\frac{10i\pi}{2}}}{1-e^{-\frac{i\pi}{2}}})$

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

2nd

$\sum_{k=0}^{N-1}e^{\frac{i2\pi kk}{2}}=\frac{1-e^{\frac{i2\pi N}{N}}}{1-e^{\frac{i2\pi}{N}}}$

$=\frac{1-1}{1-e^{\frac{i2\pi}{N}}}=0$

3th

$\sum_{n=0}^\infty (\frac{1}{2})^n cos(\frac{\pi n}{2})==\frac{1}{2}(\sum_{n=0}^\infty ((\frac{e^{\frac{i\pi n}{2}}}{2})^n+ (\frac{e^{-\frac{i\pi n}{2}}}{2})^n))$

$=\frac{1}{2}(\frac{1-0}{1-i}+\frac{1-0}{1+i})=\frac{1}{2}$

What we use?

We use that

$e^{i\pi n}=cos(\pi n)+i sin(\pi n)$

and

$\sum_{n=0}^k r^k=\frac{1-r^{k+1}}{1-r}$

6 0

3 years ago

The quotient of the opposite of a number squared and three

Mars2501 [29]

Answer:

"The quotient of the opposite of a number squared and 3"

Take "the opposite of a number squared" and call it y.

So you get "The quotient of y and 3"

This is y/3.

Now what is y? "The opposite of a number squared"

Take "The opposite of a number" and call it z.

So y is "z squared"

Replacing y, we get z^2 / 3

But what is z? "The opposite of a number"

Call "a number" x.

The opposite of x is -x.

So z is "-x"

Replacing z, we get (-x)^2 / 3

8 0

3 years ago

Express 13,040,000 in scientific notation

ser-zykov [4K]

$1.304 * 10^{7}$

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3 years ago

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Is this perpendicular, parallel, or neither?<br>y=4x+5 <br>2x+8y=16

ANEK [815]

Its perpendicular, if you need me to explain lmk

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3 years ago

What is 20 percent of 240???

Charra [1.4K]

$20\% \ of \ 240= \frac{20}{100}*240= \\\\ =20*2.4=\\\\=\boxed{48}$

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3 years ago

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