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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)

DENIUS [597]

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

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

3 0

4 years ago

Can someone explain HOW to simplify this algebraic fraction, as in tell me why and what I need to do for each step : 1-n/n^2-1

Andreyy89

- I’m assuming the expression implies the following:

(1-n)/(n^2 - 1)

The steps goes as follows:

= -(n-1)/(n^2-1) (factored a negative out)
= -(n-1)/[(n+1)(n-1)] (Factored denominator into a difference of squares, but don’t just blindly accept the fact, expand it and you should get the original denominator)

At this point, the (n-1) terms cancel, as you should know: a real number, besides 0, over itself is 1.

= -1/(n+1) , which is the answer

Note: You could also see it as 1/-(n+1) or 1/(-n-1)

8 0

3 years ago

Write a rule to describe the function shown.

I am Lyosha [343]

Answer:

y = -3x

Step-by-step explanation:

(a) Slope

y = mx + b

Choose points (-3, 9) and (3, -9)

m = (-9 - 9)/(3 – (-3))

m = -18/(3 + 3)

m = -18/6

m = -3

=====

(b) y-intercept

y = mx +b

Choose point (0,0).

0 = 0 + b

b = 0

=====

(c) Equation of line

y = mx + b

y = -3x

6 0

3 years ago

(-3) (4-5) I need help

-Dominant- [34]

Answer:

3

Step-by-step explanation:

I searched it up on the web

6 0

3 years ago

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When dividing 878 by 31, a student finds a quotient of 28 with a remainder of 11. Check the students work, and use the check to

Liula [17]

878/3 is 28 with a remainder of 10! The error is when they subtracted 258-248 wrong

3 0

3 years ago

Read 2 more answers