Find solutions of -x^2+y^2=75

Marine biologists have determined that when a shark detectsthe presence of blood in the water, it will swim in the directionin w

siniylev [52]

Solution :

a). The level curves of the function :

$C(x,y) = e^{-(x^2+2y^2)/10^4}$

are actually the curves

$e^{-(x^2+2y^2)/10^4}=k$

where k is a positive constant.

The equation is equivalent to

$x^2+2y^2=K$

$\Rightarrow \frac{x^2}{(\sqrt K)^2}+\frac{y^2}{(\sqrt {K/2})^2}=1, \text{ where}\ K = -10^4 \ln k$

which is a family of ellipses.

We sketch the level curves for K =1,2,3 and 4.

If the shark always swim in the direction of maximum increase of blood concentration, its direction at any point would coincide with the gradient vector.

Then we know the shark's path is perpendicular to the level curves it intersects.

b). We have :

$\triangledown C= \frac{\partial C}{\partial x}i+\frac{\partial C}{\partial y}j$

$\Rightarrow \triangledown C =-\frac{2}{10^4}e^{-(x^2+2y^2)/10^4}(xi+2yj),$ and

$\triangledown C$ points in the direction of most rapid increase in concentration, which means $\triangledown C$ is tangent to the most rapid increase curve.

$r(t)=x(t)i+y(t)j$ is a parametrization of the most $\text{rapid increase curve}$ , then

$\frac{dx}{dt}=\frac{dx}{dt}i+\frac{dy}{dt}j$ is a tangent to the curve.

So then we have that $\frac{dr}{dt}=\lambda \triangledown C$

$\Rightarrow \frac{dx}{dt}=-\frac{2\lambda x}{10^4}e^{-(x^2+2y^2)/10^4}, \frac{dy}{dt}=-\frac{4\lambda y}{10^4}e^{-(x^2+2y^2)/10^4}$

∴ $\frac{dy}{dx}=\frac{dy/dt}{dx/dt}=\frac{2y}{x}$

Using separation of variables,

$\frac{dy}{y}=2\frac{dx}{x}$

$\int\frac{dy}{y}=2\int \frac{dx}{x}$

$\ln y=2 \ln x$

⇒ y = kx^2 for some constant k

but we know that $y(x_0)=y_0$

$\Rightarrow kx_0^2=y_0$

$\Rightarrow k =\frac{y_0}{x_0^2}$

∴ The path of the shark will follow is along the parabola

$y=\frac{y_0}{x_0^2}x^2$

$y=y_0\left(\frac{x}{x_0}\right)^2$

7 0

2 years ago

an official playing field (including end zone) for the indoor football league has a length 39 yd longer than its width. the peri

ch4aika [34]

Answer:

42

Step-by-step explanation:

39+39 = 78

162 - 78 = 2 lengths =84

84/2 = 42

5 0

3 years ago

Question in picture solve

dimulka [17.4K]

Answer:

x= 13.5

Step-by-step explanation:

f(x) = 2x + 9

f(x) = 36

Set the 2 equations equal to each other;

2x + 9 = 36

Subtract 9 from both sides;

2x = 27

Divide both sides by 2;

x = 13.5

<em>Check:</em>

f(x) = 2x + 9

f(13.5) = 2(13.5) + 9= 27 + 9 = 36

3 0

3 years ago

The school librarian, Mr. Marker, knows the library has 1,400 books but wants to reorganize how the books are displayed on the s

kipiarov [429]

Answer:

200 resource books

800 fiction books

400 nonfiction books

Step-by-step explanation:

Let's define x as the amount of resource books that are in the library. As he has four times as many fiction books as resource books, that means he has 4*x fiction books.

We also know he has half as many nonfiction books as fiction books, that is 1/2*4*x = 2*x nonfiction books.

We just need to find out the value of x.

We know there are 1,400 books in total and there are just 3 types of books. Therefore, if we sum all of them, we get the 1,400.

Written in math language, that is

x + 4x + 2x = 1,400

7x = 1,400

We divide by 7 on both sides and we get

7/7x = 1,400/7

x = 200

Now we replace the x with 200 to know how many books he has of each type:

Resource books = x = 200

Fiction books = 4*x = 4*200 = 800

Nonfiction books = 2*x = 2*200 = 400

Therefore, there are 200 resource books, 800 fiction books and 400 nonfiction books in the library.

The tape diagram is attached as an image.

8 0

2 years ago

A fair coin is tossed 6 times. Compute the probability of tossing 6 tails in a row.

Fofino [41]

Answer:

1/6

Step-by-step explanation:

5 0

3 years ago