24 ten thousands + 11 thousands on a chart

If f(x, y, z) = x sin(yz), (a) find the gradient of f and (b) find the directional derivative of f at (2, 4, 0) in the direction

valentina_108 [34]

Answer:

a) $\nabla f(x,y,z) = \sin{yz}\mathbf{i} + xz\cos{yz}\mathbf{j} + xy \cos{yz}\mathbf{k}$ .

b) $Du_{f}(2,4,0) = -\frac{8}{\sqrt{11}}$

Step-by-step explanation:

Given a function $f(x,y,z)$ , this function has the following gradient:

$\nabla f(x,y,z) = f_{x}(x,y,z)\mathbf{i} + f_{y}(x,y,z)\mathbf{j} + f_{z}(x,y,z)\mathbf{k}$ .

(a) find the gradient of f

We have that $f(x,y,z) = x\sin{yz}$ . So

$f_{x}(x,y,z) = \sin{yz}$

$f_{y}(x,y,z) = xz\cos{yz}$

$f_{z}(x,y,z) = xy \cos{yz}$ .

$\nabla f(x,y,z) = f_{x}(x,y,z)\mathbf{i} + f_{y}(x,y,z)\mathbf{j} + f_{z}(x,y,z)\mathbf{k}$ .

$\nabla f(x,y,z) = \sin{yz}\mathbf{i} + xz\cos{yz}\mathbf{j} + xy \cos{yz}\mathbf{k}$

(b) find the directional derivative of f at (2, 4, 0) in the direction of v = i + 3j − k.

The directional derivate is the scalar product between the gradient at (2,4,0) and the unit vector of v.

We have that:

$\nabla f(x,y,z) = \sin{yz}\mathbf{i} + xz\cos{yz}\mathbf{j} + xy \cos{yz}\mathbf{k}$

$\nabla f(2,4,0) = \sin{0}\mathbf{i} + 0\cos{0}\mathbf{j} + 8 \cos{0}\mathbf{k}$ .

$\nabla f(2,4,0) = 0i+0j+8k=(0,0,8)$

The vector is $v = i + 3j - k = (1,3,-1)$

To use v as an unitary vector, we divide each component of v by the norm of v.

$|v| = \sqrt{1^{2} + 3^{2} + (-1)^{2}} = \sqrt{11}$

So

$v_{u} = (\frac{1}{\sqrt{11}}, \frac{3}{\sqrt{11}}, \frac{-1}{\sqrt{11}})$

Now, we can calculate the scalar product that is the directional derivative.

$Du_{f}(2,4,0) = (0,0,8).(\frac{1}{\sqrt{11}}, \frac{3}{\sqrt{11}}, \frac{-1}{\sqrt{11}}) = -\frac{8}{\sqrt{11}}$

6 0

3 years ago

In ΔEFG, e = 8.9 cm, f = 7.7 cm and g=2.2 cm. Find the measure of ∠F to the nearest degree.

Setler79 [48]

Answer:

51 degrees

Step-by-step explanation:

gave up on delta math

7 0

2 years ago

I need help please, I will give brainliest to the first person that answers. Also extra points.

Papessa [141]

Answer:

B)

a + c = 7

9a + 4c = $43

Step-by-step explanation:

There're 7 tickets which were bough in total. Two different types of tickets, one which represented children, the other for adults. The adult ticket is represented by a and is 9 dollars. The children's ticket is represented by c and is 4 dollars.

Have a nice April Fool's XD.

5 0

2 years ago

Find the value of y. m<1 = 3y + 6

Rufina [12.5K]

Step-by-step explanation:

$m > 1 = 3y + 6\\ \frac{m > -1 - 6}{3} = \frac{3y}{3} \\ y = \frac{m > - 5}{3}$

7 0

2 years ago

3(5+3)^2 +14 help me pls i cannot deal w my parents again

Scilla [17]

Answer:

206

Step-by-step explanation:

I put it in a calculator

6 0

3 years ago

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