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4 years ago

What percent of 21 is 7?

Mathematics

1 answer:

Mashutka [201]4 years ago

6 0

Answer:

D- 7 = x.21;33.33%

Step-by-step explanation:

p * 21 = 7

divide by 21

p = 7/21

p = .33333

multiply by 100 to get percent

p 33.333333%

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Verify the identity. cos (x - y) - cos (x + y) = 2 sin x sin y

nignag [31]

Let's start from the left side, and manipulate it to get the right side, which would prove the identity.

We know that:

i) $\displaystyle{ \cos(x-y)=\cos x \cos y+\sin x \sin y$

ii) $\displaystyle{ \cos(x+y)=\cos x \cos y-\sin x \sin y$ .

From the above fundamental identities, we can rewrite the left hand side as:

$\displaystyle{ \cos x \cos y+\sin x \sin y-(\cos x \cos y-\sin x \sin y)=$

$\displaystyle{ \cos x \cos y+\sin x \sin y-\cos x \cos y+\sin x \sin y=2\sin x \sin y$ ,

which is what we needed to show.

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3 years ago

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Step-by-step explanation:

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3 years ago

write the expression for the perimeter of rectangle with a length that is 4 centimeters longer than three times it's width.

Rina8888 [55]

Do 3 times the length. Suppose the width is 12 centimeters, 3 times that is 36 centimeters plus 4 centimeters is 40 centimers so then you do 2w+2l

4 0

4 years ago

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The diameter of a circle has endpoints (-10,5) and (-4,11)

Marta_Voda [28]

well, since we know the endpoints for the diameter, its midpoint will be where the center of the circle is located, so

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and if we get the distance between those endpoints, and take half of that, that'd be the radius of it.

$~~~~~~~~~~~~\textit{distance between 2 points} \\\\ (\stackrel{x_1}{-10}~,~\stackrel{y_1}{5})\qquad (\stackrel{x_2}{-4}~,~\stackrel{y_2}{11})\qquad \qquad d = \sqrt{( x_2- x_1)^2 + ( y_2- y_1)^2} \\\\\\ \stackrel{diameter}{d}=\sqrt{[-4 - (-10)]^2 + [11 - 5]^2}\implies d=\sqrt{(-4+10)^2+6^2} \\\\\\ d=\sqrt{6^2+6^2}\implies d=\sqrt{72}~\hfill \stackrel{radius=half~that}{\cfrac{\sqrt{72}}{2}} \\\\[-0.35em] ~\dotfill$

$\textit{equation of a circle}\\\\ (x- h)^2+(y- k)^2= r^2 \qquad center~~(\stackrel{-7}{ h},\stackrel{8}{ k})\qquad \qquad radius=\stackrel{\frac{\sqrt{72}}{2}}{ r} \\\\\\\ [x-(-7)]^2~~ + ~~[y-8]^2~~ = ~~\left( \frac{\sqrt{72}}{2} \right)^2\implies (x+7)^2~~ + ~~(y-8)^2~~ = ~~18$

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2 years ago

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matrenka [14]

Answer:

48nc

Step-by-step explanation:

The LCD of one expression is the expression itself.

7 0

4 years ago

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