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2 years ago

Cot (15 degrees)

Mathematics

1 answer:

STatiana [176]2 years ago

8 0

Answer:

Part I: cot(15 degrees) = cot(45 - 30)

Part II: Evaluation is below

Step-by-step explanation:

<em>Everything is done in degrees</em>

<em />

Two angles that differ by 15 degrees that is easy to evaluate is 30 degrees and 45 degrees. The cot(15 degrees) = cot(45 - 30) = 1/tan(45-30) = (1+tan45tan30)/(tan30 - tan45) = (1+ sqrt(3))/(sqrt(3) - 1)

We rationalize this by multiplying 1+ sqrt(3) in the top and bottom, getting:

(4 + 2sqrt(3))/2 = 2 + sqrt(3)

I hope this helps! :)

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Use spherical coordinates. evaluate xyz dv e , where e lies between the spheres ρ = 4 and ρ = 6 and above the cone ϕ = π/3.

sergey [27]

Set

$x=\rho\cos\theta\sin\varphi$

$y=\rho\sin\theta\sin\varphi$

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so that the volume element is

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The integral is then

$\displaystyle\iiint_Exyz\,\mathrm dV=\int_{\varphi=0}^{\varphi=\pi/3}\int_{\theta=0}^{\theta=2\pi}\int_{\rho=4}^{\rho=6}\rho^5\cos\theta\sin\theta\sin^3\varphi\cos\varphi\,\mathrm d\rho\,\mathrm d\theta\,\mathrm d\rho$

$=\displaystyle\left(\int_0^{\pi/3}\sin^3\varphi\cos\varphi\,\mathrm d\varphi\right)\underbrace{\left(\int_0^{2\pi}\cos\theta\sin\theta\,\mathrm d\theta\right)}_0\left(\int_4^6\rho^5\,\mathrm d\rho\right)$

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In a large population, 60 % of the people have been vaccinated. If 5 people are randomly selected, what is the probability that

Delvig [45]

<h3>Answer: 0.98976</h3>

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60% of the people have been vaccinated, so 40% have not.

The probability of getting five people in a row that aren't vaccinated is (0.40)^5 = 0.01024

Subtract this from 1 to get the probability of at least one vaccinated person in the sample of five.

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This works because the events "at least one vaccinated" and "none vaccinated" are complementary. One or the other must happen, which means the two probabilities add to 1.

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