Calculus 1 : How to find differential functions

Study concepts, example questions & explanations for Calculus 1

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Example Questions

Example Question #481 : How To Find Differential Functions

Find the divergence of the function \displaystyle F(x,y,z)=x^2y\widehat{i}+3yz^2\widehat{j}+xz\widehat{k} at \displaystyle (2,4,5)

Hint: \displaystyle divF(x_1,x_2,...x_n)=\frac{\delta F_{x_1}}{\delta x_1}+\frac{\delta F_{x_2}}{\delta x_2}+...+\frac{\delta F_{x_n}}{\delta x_n}

Possible Answers:

\displaystyle 19

\displaystyle 72

\displaystyle 93

\displaystyle 118

\displaystyle 42

Correct answer:

\displaystyle 93

Explanation:

Divergence can be viewed as a measure of the magnitude of a vector field's source or sink at a given point.

To visualize this, picture an open drain in a tub full of water; this drain may represent a 'sink,' and all of the velocities at each specific point in the tub represent the vector field. Close to the drain, the velocity will be greater than a spot farther away from the drain.

What divergence can calculate is what this velocity is at a given point. Again, the magnitude of the vector field.

We're given the function

 \displaystyle F(x,y,z)=x^2y\widehat{i}+3yz^2\widehat{j}+xz\widehat{k}

What we will do is take the derivative of each vector element with respect to its variable \displaystyle (\widehat{i}:x,\widehat{j}:y,\widehat{k}:z)

Then sum the results together:

 \displaystyle divF(x,y,z)=2xy+3z^2+x

At the point \displaystyle (2,4,5)

\displaystyle divF(2,4,5)=2(2)(4)+3(5)^2+2

\displaystyle divF(2,4,5)=93

Example Question #482 : How To Find Differential Functions

Find the divergence of the function \displaystyle F(x,y,z)=4xyz\widehat{i}+2y^2z\widehat{j}+12x^2y\widehat{k} at \displaystyle (4,1,3)

Hint: \displaystyle divF(x_1,x_2,...x_n)=\frac{\delta F_{x_1}}{\delta x_1}+\frac{\delta F_{x_2}}{\delta x_2}+...+\frac{\delta F_{x_n}}{\delta x_n}

Possible Answers:

\displaystyle 42

\displaystyle 24

\displaystyle 13

\displaystyle 7

\displaystyle 33

Correct answer:

\displaystyle 24

Explanation:

Divergence can be viewed as a measure of the magnitude of a vector field's source or sink at a given point.

To visualize this, picture an open drain in a tub full of water; this drain may represent a 'sink,' and all of the velocities at each specific point in the tub represent the vector field. Close to the drain, the velocity will be greater than a spot farther away from the drain.

What divergence can calculate is what this velocity is at a given point. Again, the magnitude of the vector field.

We're given the function

 \displaystyle F(x,y,z)=4xyz\widehat{i}+2y^2z\widehat{j}+12x^2y\widehat{k}

What we will do is take the derivative of each vector element with respect to its variable \displaystyle (\widehat{i}:x,\widehat{j}:y,\widehat{k}:z)

Then sum the results together:

\displaystyle divF(x,y,z)=4yz+4yz+0=8yz 

At the point \displaystyle (4,1,3)

\displaystyle divF(4,1,3)=8(1)(3)=24

Example Question #483 : How To Find Differential Functions

Find the divergence of the function \displaystyle F(x,y)=x^2e^y\widehat{i}+5ye^x\widehat{j} at \displaystyle (-1,2)

Hint: \displaystyle divF(x_1,x_2,...x_n)=\frac{\delta F_{x_1}}{\delta x_1}+\frac{\delta F_{x_2}}{\delta x_2}+...+\frac{\delta F_{x_n}}{\delta x_n}

Possible Answers:

\displaystyle -23.22

\displaystyle -5.12

\displaystyle -12.94

\displaystyle -15.88

\displaystyle 8.76

Correct answer:

\displaystyle -12.94

Explanation:

Divergence can be viewed as a measure of the magnitude of a vector field's source or sink at a given point.

To visualize this, picture an open drain in a tub full of water; this drain may represent a 'sink,' and all of the velocities at each specific point in the tub represent the vector field. Close to the drain, the velocity will be greater than a spot farther away from the drain.

What divergence can calculate is what this velocity is at a given point. Again, the magnitude of the vector field.

We're given the function

\displaystyle F(x,y)=x^2e^y\widehat{i}+5ye^x\widehat{j} 

What we will do is take the derivative of each vector element with respect to its variable \displaystyle (\widehat{i}:x,\widehat{j}:y,\widehat{k}:z)

Then sum the results together:

\displaystyle d(e^u)=e^udu

\displaystyle divF(x,y)=2xe^y+5e^x

At the point \displaystyle (-1,2)

\displaystyle divF(-1,2)=2(-1)e^2+5e^{-1}

\displaystyle divF(-1,2)=-12.94

Example Question #671 : Functions

Find the divergence of the function \displaystyle F(x,y)=xcos(y)\widehat{i}+xcos(y)\widehat{j} at \displaystyle (\pi,\pi)

Hint: \displaystyle divF(x_1,x_2,...x_n)=\frac{\delta F_{x_1}}{\delta x_1}+\frac{\delta F_{x_2}}{\delta x_2}+...+\frac{\delta F_{x_n}}{\delta x_n}

Possible Answers:

\displaystyle 1

\displaystyle \pi

\displaystyle 0

\displaystyle 1+\pi

\displaystyle 1-\pi

Correct answer:

\displaystyle 1

Explanation:

Divergence can be viewed as a measure of the magnitude of a vector field's source or sink at a given point.

To visualize this, picture an open drain in a tub full of water; this drain may represent a 'sink,' and all of the velocities at each specific point in the tub represent the vector field. Close to the drain, the velocity will be greater than a spot farther away from the drain.

What divergence can calculate is what this velocity is at a given point. Again, the magnitude of the vector field.

We're given the function

\displaystyle F(x,y)=xcos(y)\widehat{i}+xcos(y)\widehat{j} 

What we will do is take the derivative of each vector element with respect to its variable \displaystyle (\widehat{i}:x,\widehat{j}:y,\widehat{k}:z)

\displaystyle d(cos(u))=-sin(u)du

Then sum the results together:

\displaystyle divF(x,y)=cos(y)-xsin(y)

At the point \displaystyle (\pi,\pi)

\displaystyle divF(\pi,\pi)=cos(\pi)-\pi sin(\pi)

\displaystyle divF(\pi,\pi)=1

Example Question #671 : Functions

Find the divergence of the function \displaystyle F(x,y)=x^2cos(y)\widehat{i}+x^2sin(y)\widehat{j} at \displaystyle (3,2\pi)

Hint: \displaystyle divF(x_1,x_2,...x_n)=\frac{\delta F_{x_1}}{\delta x_1}+\frac{\delta F_{x_2}}{\delta x_2}+...+\frac{\delta F_{x_n}}{\delta x_n}

Possible Answers:

\displaystyle 6

\displaystyle 3

\displaystyle 15

\displaystyle -3

\displaystyle 9

Correct answer:

\displaystyle 15

Explanation:

Divergence can be viewed as a measure of the magnitude of a vector field's source or sink at a given point.

To visualize this, picture an open drain in a tub full of water; this drain may represent a 'sink,' and all of the velocities at each specific point in the tub represent the vector field. Close to the drain, the velocity will be greater than a spot farther away from the drain.

What divergence can calculate is what this velocity is at a given point. Again, the magnitude of the vector field.

We're given the function

\displaystyle F(x,y)=x^2cos(y)\widehat{i}+x^2sin(y)\widehat{j} 

What we will do is take the derivative of each vector element with respect to its variable \displaystyle (\widehat{i}:x,\widehat{j}:y,\widehat{k}:z)

Then sum the results together:

\displaystyle d(sin(u))=cos(u)du

\displaystyle divF(x,y)=2xcos(y)+x^2cos(y) 

At the point \displaystyle (3,2\pi)

\displaystyle divF(3,2\pi)=2(3)cos(2\pi)+3^2cos(2\pi)=6+9=15

Example Question #673 : Functions

Find the divergence of the function \displaystyle F(x,y)=e^xln(y)\widehat{i}+cos(x)sin(y)\widehat{j} at \displaystyle (2,0.2)

Hint: \displaystyle divF(x_1,x_2,...x_n)=\frac{\delta F_{x_1}}{\delta x_1}+\frac{\delta F_{x_2}}{\delta x_2}+...+\frac{\delta F_{x_n}}{\delta x_n}

Possible Answers:

\displaystyle -6.6

\displaystyle -12.3

\displaystyle -1.2

\displaystyle 5.9

\displaystyle 11.8

Correct answer:

\displaystyle -12.3

Explanation:

Divergence can be viewed as a measure of the magnitude of a vector field's source or sink at a given point.

To visualize this, picture an open drain in a tub full of water; this drain may represent a 'sink,' and all of the velocities at each specific point in the tub represent the vector field. Close to the drain, the velocity will be greater than a spot farther away from the drain.

What divergence can calculate is what this velocity is at a given point. Again, the magnitude of the vector field.

We're given the function

\displaystyle F(x,y)=e^xln(y)\widehat{i}+cos(x)sin(y)\widehat{j} 

What we will do is take the derivative of each vector element with respect to its variable \displaystyle (\widehat{i}:x,\widehat{j}:y,\widehat{k}:z)

Then sum the results together:

\displaystyle d(e^u)=e^udu

\displaystyle d(sin(u))=cos(u)du

\displaystyle div F(x,y)=e^xln(y)+cos(x)cos(y)

At the point \displaystyle (2,0.2)

\displaystyle div F(2,0.2)=e^2ln(0.2)+cos(2)cos(0.2)=-12.3

Example Question #482 : How To Find Differential Functions

Find the divergence of the function \displaystyle F(x,y)=18xy^2\widehat{i}+21x^2y\widehat{j} at \displaystyle (0.2,0.1)

Hint: \displaystyle divF(x_1,x_2,...x_n)=\frac{\delta F_{x_1}}{\delta x_1}+\frac{\delta F_{x_2}}{\delta x_2}+...+\frac{\delta F_{x_n}}{\delta x_n}

Possible Answers:

\displaystyle 3.12

\displaystyle 1.02

\displaystyle 10.2

\displaystyle 20.4

Correct answer:

\displaystyle 1.02

Explanation:

Divergence can be viewed as a measure of the magnitude of a vector field's source or sink at a given point.

To visualize this, picture an open drain in a tub full of water; this drain may represent a 'sink,' and all of the velocities at each specific point in the tub represent the vector field. Close to the drain, the velocity will be greater than a spot farther away from the drain.

What divergence can calculate is what this velocity is at a given point. Again, the magnitude of the vector field.

We're given the function

\displaystyle F(x,y)=18xy^2\widehat{i}+21x^2y\widehat{j} 

What we will do is take the derivative of each vector element with respect to its variable \displaystyle (\widehat{i}:x,\widehat{j}:y,\widehat{k}:z)

Then sum the results together:

\displaystyle divF(x,y)=18y^2+21x^2

At the point  \displaystyle (0.2,0.1)

\displaystyle divF(0.2,0.1)=18(0.1)^2+21(0.2)^2=1.02

Example Question #675 : Functions

Find the divergence of the function \displaystyle F(x,y)=sin(xy^2)\widehat{i}+e^ycos(2x)\widehat{j} at \displaystyle (3,1)

Hint: \displaystyle divF(x_1,x_2,...x_n)=\frac{\delta F_{x_1}}{\delta x_1}+\frac{\delta F_{x_2}}{\delta x_2}+...+\frac{\delta F_{x_n}}{\delta x_n}

Possible Answers:

\displaystyle 3.95

\displaystyle 2.62

\displaystyle 1.18

\displaystyle 1.62

\displaystyle 4.44

Correct answer:

\displaystyle 1.62

Explanation:

Divergence can be viewed as a measure of the magnitude of a vector field's source or sink at a given point.

To visualize this, picture an open drain in a tub full of water; this drain may represent a 'sink,' and all of the velocities at each specific point in the tub represent the vector field. Close to the drain, the velocity will be greater than a spot farther away from the drain.

What divergence can calculate is what this velocity is at a given point. Again, the magnitude of the vector field.

We're given the function

\displaystyle F(x,y)=sin(xy^2)\widehat{i}+e^ycos(2x)\widehat{j}

What we will do is take the derivative of each vector element with respect to its variable \displaystyle (\widehat{i}:x,\widehat{j}:y,\widehat{k}:z)

Then sum the results together:

Derivative of an exponential: 

\displaystyle d[e^u]=e^udu

Trigonometric derivative: 

\displaystyle d[sin(u)]=cos(u)du

Note that u may represent large functions, and not just individual variables!

\displaystyle divF(x,y)=y^2cos(xy^2)+e^ycos(2x)

At the point \displaystyle (3,1)

\displaystyle divF(3,1)=1^2cos(3(1)^2)+e^1cos(2(3))=1.62

Example Question #673 : Functions

Find the divergence of the function \displaystyle F(x,y)=x^y\widehat{i}+y^x\widehat{j} at \displaystyle (2,3)

Hint: \displaystyle divF(x_1,x_2,...x_n)=\frac{\delta F_{x_1}}{\delta x_1}+\frac{\delta F_{x_2}}{\delta x_2}+...+\frac{\delta F_{x_n}}{\delta x_n}

Possible Answers:

\displaystyle 14.2

\displaystyle 18

\displaystyle 3.7

\displaystyle 9

\displaystyle 16.2

Correct answer:

\displaystyle 18

Explanation:

Divergence can be viewed as a measure of the magnitude of a vector field's source or sink at a given point.

To visualize this, picture an open drain in a tub full of water; this drain may represent a 'sink,' and all of the velocities at each specific point in the tub represent the vector field. Close to the drain, the velocity will be greater than a spot farther away from the drain.

What divergence can calculate is what this velocity is at a given point. Again, the magnitude of the vector field.

We're given the function

\displaystyle F(x,y)=x^y\widehat{i}+y^x\widehat{j}

What we will do is take the derivative of each vector element with respect to its variable \displaystyle (\widehat{i}:x,\widehat{j}:y,\widehat{k}:z)

Then sum the results together:

\displaystyle divF(x,y)=yx^{y-1}+xy^{x-1}

At the point \displaystyle (2,3)

\displaystyle divF(2,3)=(3)(2^{3-1})+(2)(3^{2-1})=18

Example Question #677 : Functions

Find the divergence of the function \displaystyle F(x,y)=y^x\widehat{i}+x^y\widehat{j} at \displaystyle (2,3)

Hint: \displaystyle divF(x_1,x_2,...x_n)=\frac{\delta F_{x_1}}{\delta x_1}+\frac{\delta F_{x_2}}{\delta x_2}+...+\frac{\delta F_{x_n}}{\delta x_n}

Possible Answers:

\displaystyle 9

\displaystyle 18

\displaystyle 12.2

\displaystyle 15.4

\displaystyle 7.9

Correct answer:

\displaystyle 15.4

Explanation:

Divergence can be viewed as a measure of the magnitude of a vector field's source or sink at a given point.

To visualize this, picture an open drain in a tub full of water; this drain may represent a 'sink,' and all of the velocities at each specific point in the tub represent the vector field. Close to the drain, the velocity will be greater than a spot farther away from the drain.

What divergence can calculate is what this velocity is at a given point. Again, the magnitude of the vector field.

We're given the function

\displaystyle F(x,y)=y^x\widehat{i}+x^y\widehat{j}

What we will do is take the derivative of each vector element with respect to its variable \displaystyle (\widehat{i}:x,\widehat{j}:y,\widehat{k}:z)

Then sum the results together:

Derivative of an exponential: 

\displaystyle d[a^u]=a^uduln(a)

Note that u may represent large functions, and not just individual variables!

\displaystyle divF(x,y)=y^xln(y)+x^yln(x)

At the point \displaystyle (2,3)

\displaystyle divF(2,3)=3^2ln(3)+2^3ln(2)=15.4

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