Mathematics, 16.07.2019 01:30 jordonlewis

Use the chain rule to find dw/dt. w = ln x2 + y2 + z2 , x = 7 sin(t), y = 9 cos(t), z = 6 tan(t)

Answers: 1

Show answers

Answers

Answer from: Meliiiii

Using the chain rule, we find that:

$\frac{dw}{dt} = \frac{1}{49\sin^{2}{t} + 81\cos^2t + 36\tan^2t}(-64\sin{t}\cos{t} + 72\tan{t}\sec^2{t})$

The function w is:

$w(x,y,z) = \ln{x^2 + y^2 + z^2}$

x, y and z are functions of t, given by:

$x(t) = 7\sin{t}$

$y(t) = 9\cos{t}$

$z(t) = 6\tan{t}$

Thus, by the chain rule:

$\frac{dw}{dt} = \frac{dw}{dx}\frac{dx}{dt} + \frac{dw}{dy}\frac{dy}{dt} + \frac{dw}{dz}\frac{dz}{dt}$

The derivatives are:

$\frac{dw}{dx} = \frac{2x}{x^2 + y^2 + z^2} = \frac{14\sin{t}}{49\sin^{2}{t} + 81\cos^2t + 36\tan^2t}$

$\frac{dx}{dt} = 7\cos{t}$

$\frac{dw}{dy} = \frac{2y}{x^2 + y^2 + z^2} = \frac{18\cos{t}}{49\sin^{2}{t} + 81\cos^2t + 36\tan^2t}$

$\frac{dy}{dt} = -9\sin{t}$

$\frac{dw}{dz} = \frac{2z}{x^2 + y^2 + z^2} = \frac{12\tan{t}}{49\sin^{2}{t} + 81\cos^2t + 36\tan^2t}$

$\frac{dy}{dt} = 6\sec^2{t}$

Then:

$\frac{dw}{dt} = \frac{dw}{dx}\frac{dx}{dt} + \frac{dw}{dy}\frac{dy}{dt} + \frac{dw}{dz}\frac{dz}{dt}$

$\frac{dw}{dt} = \frac{1}{49\sin^{2}{t} + 81\cos^2t + 36\tan^2t}(98\sin{t}\cos{t} - 162\sin{t}\cos{t} + 72\tan{t}\sec^2{t})$

$\frac{dw}{dt} = \frac{1}{49\sin^{2}{t} + 81\cos^2t + 36\tan^2t}(-64\sin{t}\cos{t} + 72\tan{t}\sec^2{t})$

A similar problem is given at link

Answer from: t779

By the chain rule,

$\dfrac{\mathrm dw}{\mathrm dt}=\dfrac{\partial w}{\partial x}\dfrac{\mathrm dx}{\mathrm dt}+\dfrac{\partial w}{\partial y}\dfrac{\mathrm dy}{\mathrm dt}+\dfrac{\partial w}{\partial z}\dfrac{\mathrm dz}{\mathrm dt}$

We have

$\dfrac{\partial w}{\partial x}=\dfrac{2x}{x^2+y^2+z^2}$
$\dfrac{\partial w}{\partial y}=\dfrac{2y}{x^2+y^2+z^2}$
$\dfrac{\partial w}{\partial z}=\dfrac{2z}{x^2+y^2+z^2}$

$\dfrac{\mathrm dx}{\mathrm dt}=7\cos t$
$\dfrac{\mathrm dy}{\mathrm dt}=-9\sin t$
$\dfrac{\mathrm dz}{\mathrm dt}=6\sec^2t$

So we have

$\dfrac{\mathrm dw}{\mathrm dt}=\dfrac2{x^2+y^2+z^2}\left(7x\cos t-9y\sin t+6z\sec^2t\right)$
$\dfrac{\mathrm dw}{\mathrm dt}=\dfrac{2\left(49\sin t\cos t-81\cos t\sin t+36\tan t\sec^2t\right)}{49\sin^2t+81\cos^2t+36\tan^2t}$
$\dfrac{\mathrm dw}{\mathrm dt}=\dfrac{8\sin t(9-16\cos^4t)}{\cos t(36+13\cos^2t+32\cos^4t)}$

Answer from: Quest

1. f(x)=x²+10x+16

use the formula to find the vertex = (-b/2a, f(-b/2a)) , here in the above equation a=1(as, a> 0 the parabola is open upward), b=10. by putting the values.

-b/2a = -10/2(1) = -5

f(-b/2a)= f(-5)= (-5)²+10(-5)+16= -9

so, vertex = (-5, -9)

now, find y- intercept put x=0 in the above equation. f(0)= 0+0+16, we get point (0,16).

now find x-intercept put y=0 in the above equation. 0= x²+10x+16

x²+10x+16=0 ⇒x²+8x+2x+16=0 ⇒x(x+8)+2(x+8)=0 ⇒(x+8)(x+2)=0 ⇒x=-8 , x=-2

from vertex, y-intercept and x-intercept you can easily plot the graph of given parabolic equation. the graph is attached below.

2. f(x)=−(x−3)(x+1)

by multiplying the factors, the general form is f(x)= -x²+2x+3.

use the formula to find the vertex = (-b/2a, f(-b/2a)) , here in the above equation a=-1(as, a< 0 the parabola is open downward), b=2. by putting the values.

-b/2a = -2/2(-1) = 1

f(-b/2a)= f(1)=-(1)²+2(1)+3= 4

so, vertex = (1, 4)

now, find y- intercept put x=0 in the above equation. f(0)= 0+0+3, we get point (0, 3).

now find x-intercept put y=0 in the above equation. 0= -x²+2x+3.

-x²+2x+3=0 the factor form is already given in the question so, ⇒-(x-3)(x+1)=0 ⇒x=3 , x=-1

from vertex, y-intercept and x-intercept you can easily plot the graph of given parabolic equation. the graph is attached below.

3. f(x)= −x²+4

use the formula to find the vertex = (-b/2a, f(-b/2a)) , here in the above equation a=-1(as, a< 0 the parabola is open downward), b=0. by putting the values.

-b/2a = -0/2(-1) = 0

f(-b/2a)= f(0)= −(0)²+4 =4

so, vertex = (0, 4)

now, find y- intercept put x=0 in the above equation. f(0)= −(0)²+4, we get point (0, 4).

now find x-intercept put y=0 in the above equation. 0= −x²+4

−x²+4=0 ⇒-(x²-4)=0 ⇒ -(x-2)(x+2)=0 ⇒x=2 , x=-2

from vertex, y-intercept and x-intercept you can easily plot the graph of given parabolic equation. the graph is attached below.

4. f(x)=2x²+16x+30

use the formula to find the vertex = (-b/2a, f(-b/2a)) , here in the above equation a=2(as, a> 0 the parabola is open upward), b=16. by putting the values.

-b/2a = -16/2(2) = -4

f(-b/2a)= f(-4)= 2(-4)²+16(-4)+30 = -2

so, vertex = (-4, -2)

now, find y- intercept put x=0 in the above equation. f(0)= 0+0+30, we get point (0, 30).

now find x-intercept put y=0 in the above equation. 0=2x²+16x+30

2x²+16x+30=0 ⇒2(x²+8x+15)=0 ⇒x²+8x+15=0 ⇒x²+5x+3x+15=0 ⇒x(x+5)+3(x+5)=0 ⇒(x+5)(x+3)=0 ⇒x=-5 , x= -3

from vertex, y-intercept and x-intercept you can easily plot the graph of given parabolic equation. the graph is attached below.

5. y=(x+2)²+4

the general form of parabola is y=a(x-h)²+k , where vertex = (h,k)

if a> 0 parabola is opened upward.

if a< 0 parabola is opened downward.

compare the given equation with general form of parabola.

-h=2 ⇒h=-2

k=4

so, vertex= (-2, 4)

as, a=1 which is greater than 0 so parabola is opened upward and the graph has minimum.

hope this : )

Use the parabola tool to graph the quadratic function f(x) = -2(x+4)2 - 3 graph the parabola by firs

Answer from: Quest

Google it that might work
Abc is similar to lmn. also side ab measures 5 cm , side ac measures 7 cm, and side lm measures 35 c

Another question on Mathematics

Mathematics, 21.06.2019 14:30

Which expression is equivalent to (3^2)^-2 a.-81 b.-12 c.1/81 d.1/12

Answers: 2

Answer

Mathematics, 21.06.2019 21:00

*let m∠cob = 50°30’, m∠aob = 70° and m∠aoc = 20°30’. could point c be in the interior of ∠aob? why?

Answers: 1

Answer

Mathematics, 21.06.2019 21:30

Cal's go cart has a gas tank with the dimensions shown below. he uses a gas can that holds 11 gallon of gas, to fill the go cart tank. 11 gallon = 231 inches^3 how many full gas cans will it take to fill the go cart's gas tank?

Answers: 3

Answer

Mathematics, 21.06.2019 21:40

Asystem of linear equations contains two equations with the same slope. select all of the correct statements. i a. the system may have two solutions. - b. the system may have infinitely many solutions. c. the system may have one solution. o d. the system may have no solution. submit

Answers: 3

Answer

You know the right answer?

Use the chain rule to find dw/dt. w = ln x2 + y2 + z2 , x = 7 sin(t), y = 9 cos(t), z = 6 tan(t)...

Questions