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seraphim [82]
3 years ago
7

Find the exact area of the surface obtained by rotating the curve about the x-axis.

Mathematics
1 answer:
padilas [110]3 years ago
5 0
\bf \begin{cases}
y=sin\left( \frac{\pi x}{6} \right)\\
0\le x\le 6\\
\textit{about the x-axis, or }y=0
\end{cases}\\\\
-----------------------------\\\\
\textit{using the disc method}
\\\\
V=\int\limits_{0}^{6}\pi \left[ sin\left( \frac{\pi x}{6} \right) \right]^2\cdot dx\implies \pi\int\limits_{0}^{6} \left[ sin\left( \frac{\pi x}{6} \right) \right]^2\cdot dx
\\\\\\
 \pi\int\limits_{0}^{6} sin^2\left( \frac{\pi x}{6} \right) \cdot dx\\\\
-----------------------------\\\\

\bf \textit{now, let us check the double angle identities}
\\\\
cos(2\theta)=
\begin{cases}
cos^2(\theta)-sin^2(\theta)\\
\boxed{1-2sin^2(\theta)}\\
2cos^2(\theta)-1
\end{cases}
\\\\\\
thus\implies cos(2\theta)=1-2sin^2(\theta)\implies 2sin^2(\theta)=1-cos(2\theta)
\\\\\\
sin^2(\theta)=\cfrac{1-cos(2\theta)}{2}\qquad thus\\\\
-----------------------------

\bf \pi\int\limits_{0}^{6} \left[ sin\left( \frac{\pi x}{6} \right) \right]^2\cdot dx\implies 
\pi\int\limits_{0}^{6} \cfrac{1-cos\left(2\cdot  \frac{\pi x}{6} \right)}{2}\cdot dx
\\\\\\
\pi\int\limits_{0}^{6}\cfrac{1}{2}dx-\pi \cdot \cfrac{1}{2}\pi\int\limits_{0}^{6}cos\left(\frac{\pi x}{3} \right)dx
\\\\\\
\left[\cfrac{\pi x}{2}-\cfrac{\pi }{2}\cdot \cfrac{sin\left(\frac{\pi x}{3} \right)}{\frac{\pi x}{3} }  \right]\implies \left[ \cfrac{\pi }{2}x-\cfrac{3sin\left(\frac{\pi x}{3} \right)}{2x} \right]_0^6

and surely, you'd know how to get the values for the bounds there

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D. You need to take geometry so you will learn how to drive farther and faster.

Step-by-step explanation:

Geometry can help you earn credit and teach you real-world skills that can even be applied to a future career of your choice!

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Pls,pls,pls,help me I will give lots of pound 100+ points
Bond [772]

Answer:

  1. 3log(10) -2log(5) ≈ 1.60206
  2. no; rules of logs apply to any base. ln(x) ≈ 2.302585×log(x)
  3. no; the given "property" is nonsense

Step-by-step explanation:

<h3>1.</h3>

The given expression expression can be simplified to ...

  3log(10) -2log(5) = log(10^3) -log(5^2) = log(1000) -log(25)

  = log(1000/25) = log(40) . . . . ≠ log(5)

  ≈ 1.60206

Or, it can be evaluated directly:

  = 3(1) -2(0.69897) = 3 -1.39794

  = 1.60206

__

<h3>2.</h3>

The properties of logarithms apply to logarithms of any base. Natural logs and common logs are related by the change of base formula ...

  ln(x) = log(x)/log(e) ≈ 2.302585·log(x)

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<h3>3.</h3>

The given "property" is nonsense. There is no simplification for the product of logs of the same base. There is no expansion for the log of a sum. The formula for the log of a power does apply:

  \log(a)\log(b)=\log(a^{\log(b)})=\log(b^{\log(a)})

Numerical evaluation of Mr. Kim's expression would prove him wrong.

  log(3)log(4) = (0.47712)(0.60206) = 0.28726

  log(7) = 0.84510

  0.28726 ≠ 0.84510

  log(3)log(4) ≠ log(7)

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I just want you to know have a good day
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Answer:

Thank you very much :) needed that

6 0
3 years ago
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Firlakuza [10]

Answer:

(0,-3)

Step-by-step explanation:

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Angle D has what measurement according to the protractor?
Aliun [14]

Answer:

B. 90^o

Step-by-step explanation:

We have been given a protractor and we are asked to find the measure of angle D.

We can see from our given protractor that the measure of angle D is 90 degrees as the ray OD crosses our protractor at 90 degrees.

Therefore, the measure of angle D is 90 degrees and option B is the correct choice.

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