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3 years ago

The length of a rectangle is 2 meters less than 2 times the width. The perimeter is 20 meters. Find the width.

1 answer:

4 0

The equation you'd make would be (2x-2)+(2x-2)+x+x=20 because the length is 2 m less than the width (x). To simplify, it'd be 6x-4=20 because you combine like terms. You then move the -4 over to the 20 to make it 6x=24. The final answer is 4 meters.

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G find the area of the surface over the given region. use a computer algebra system to verify your results. the sphere r(u,v) =

Svetach [21]

Presumably you should be doing this using calculus methods, namely computing the surface integral along $\mathbf r(u,v)$ .

But since $\mathbf r(u,v)$ describes a sphere, we can simply recall that the surface area of a sphere of radius $a$ is $4\pi a^2$ .

In calculus terms, we would first find an expression for the surface element, which is given by

$\displaystyle\iint_S\mathrm dS=\iint_S\left\|\frac{\partial\mathbf r}{\partial u}\times\frac{\partial\mathbf r}{\partial v}\right\|\,\mathrm du\,\mathrm dv$

$\dfrac{\partial\mathbf r}{\partial u}=a\cos u\cos v\,\mathbf i+a\cos u\sin v\,\mathbf j-a\sin u\,\mathbf k$
$\dfrac{\partial\mathbf r}{\partial v}=-a\sin u\sin v\,\mathbf i+a\sin u\cos v\,\mathbf j$
$\implies\dfrac{\partial\mathbf r}{\partial u}\times\dfrac{\partial\mathbf r}{\partial v}=a^2\sin^2u\cos v\,\mathbf i+a^2\sin^2u\sin v\,\mathbf j+a^2\sin u\cos u\,\mathbf k$
$\implies\left\|\dfrac{\partial\mathbf r}{\partial u}\times\dfrac{\partial\mathbf r}{\partial v}\right\|=a^2\sin u$

So the area of the surface is

$\displaystyle\iint_S\mathrm dS=\int_{u=0}^{u=\pi}\int_{v=0}^{v=2\pi}a^2\sin u\,\mathrm dv\,\mathrm du=2\pi a^2\int_{u=0}^{u=\pi}\sin u$
$=-2\pi a^2(\cos\pi-\cos 0)$
$=-2\pi a^2(-1-1)$
$=4\pi a^2$

as expected.

6 0

2 years ago

Need help with this

cupoosta [38]

a²+b² = c² where a and b are legs and c is the hypotenuse

So...

a²+4²=13²

a²+16=169

a²=153

a=√153

answer: approx. 12.37 units

7 0

3 years ago

Read 2 more answers

the present age of the father is twice HD old is the age of its own three years hence if two years hence the age of the father w

NemiM [27]

Big sundi and more bigger with spice

6 0

2 years ago

help Bob divide his water plants for the outer four aquariums. Insert images of the plant in the space below to show how you can

dexar [7]

Answer:

The Answer is 4.5 or 4 1/2

Step-by-step explanation:

3 0

3 years ago

In an inductive generalization, in order to achieve an error margin of plus or minus 3 percentage points at a confidence level o

ANTONII [103]

Let n = required random sample size.

Assume that the population standard deviation is known as σ.
Let m = sample mean.
At the 95% confidence level, the expected range is
(m - k(σ/√n), m + k(σ/√n))
where k = 1.96.

Therefore the error margin is 1.96(σ/√n).
Because the error margin is specified as 3% or 0.03, therefore
(1.96σ)/√n = 0.03
√n = (1.96σ)/0.03
n = 128.05σ²

This means that the sample size is about 128 times the population variance.

Answer:
Smallest sample size = 128.05σ², where σ = population standard deviation.

6 0

2 years ago