Calculus 3 : Calculus 3

Study concepts, example questions & explanations for Calculus 3

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Example Questions

Example Question #39 : Cylindrical Coordinates

A point in space is located, in Cartesian coordinates, at \displaystyle (6,6,-6). What is the position of this point in cylindrical coordinates?

Possible Answers:

\displaystyle (8.49,135^{\circ},-6)

\displaystyle (8.49,-135^{\circ},-6)

\displaystyle (12,135^{\circ},-6)

\displaystyle (8.49,-45^{\circ},-6)

\displaystyle (8.49,45^{\circ},-6)

Correct answer:

\displaystyle (8.49,45^{\circ},-6)

Explanation:

When given Cartesian coordinates of the form \displaystyle (x,y,z) to cylindrical coordinates of the form \displaystyle (r,\theta,z), the first and third terms are the most straightforward.

\displaystyle r=\sqrt{x^2+y^2}

\displaystyle z=z

Care should be taken, however, when calculating \displaystyle \theta. The formula for it is as follows: 

\displaystyle \theta=arctan(\frac{y}{x})

However, it is important to be mindful of the signs of both \displaystyle y and \displaystyle x, bearing in mind which quadrant the point lies; this will determine the value of \displaystyle \theta:

Quadrants

It is something to bear in mind when making a calculation using a calculator; negative \displaystyle y values by convention create a negative \displaystyle \theta, while negative \displaystyle x values lead to \displaystyle |\theta|>90^{\circ};\frac{\pi}{2}

For our coordinates \displaystyle (6,6,-6)

\displaystyle \begin{align*}&r=6^2+6^2=8.49\\&\theta=arctan(\frac{6}{6})=45^{\circ}\\&z=-6\end{align*}

Example Question #40 : Cylindrical Coordinates

A point in space is located, in Cartesian coordinates, at \displaystyle (-9,7,-4). What is the position of this point in cylindrical coordinates?

Possible Answers:

\displaystyle (11.4,142.13^{\circ},-4)

\displaystyle (11.4,37.87^{\circ},-4)

\displaystyle (11.4,-142.13^{\circ},-4)

\displaystyle (-2,142.13^{\circ},-4)

\displaystyle (-2,37.87^{\circ},-4)

Correct answer:

\displaystyle (11.4,142.13^{\circ},-4)

Explanation:

When given Cartesian coordinates of the form \displaystyle (x,y,z) to cylindrical coordinates of the form \displaystyle (r,\theta,z), the first and third terms are the most straightforward.

\displaystyle r=\sqrt{x^2+y^2}

\displaystyle z=z

Care should be taken, however, when calculating \displaystyle \theta. The formula for it is as follows: 

\displaystyle \theta=arctan(\frac{y}{x})

However, it is important to be mindful of the signs of both \displaystyle y and \displaystyle x, bearing in mind which quadrant the point lies; this will determine the value of \displaystyle \theta:

Quadrants

It is something to bear in mind when making a calculation using a calculator; negative \displaystyle y values by convention create a negative \displaystyle \theta, while negative \displaystyle x values lead to \displaystyle |\theta|>90^{\circ};\frac{\pi}{2}

For our coordinates \displaystyle (-9,7,-4)

\displaystyle \begin{align*}&r=\sqrt{(-9)^2+(7)^2}=11.4\\&\theta=arctan(\frac{7}{-9})=142.13^{\circ}\\&z=-4\end{align*}

Example Question #41 : Cylindrical Coordinates

A point in space is located, in Cartesian coordinates, at \displaystyle (8,1,7). What is the position of this point in cylindrical coordinates?

Possible Answers:

\displaystyle (8.06,-172.87^{\circ},7)

\displaystyle (8.06,172.87^{\circ},7)

\displaystyle (8.06,-7.13^{\circ},7)

\displaystyle (9,172.87^{\circ},7)

\displaystyle (8.06,7.13^{\circ},7)

Correct answer:

\displaystyle (8.06,7.13^{\circ},7)

Explanation:

When given Cartesian coordinates of the form \displaystyle (x,y,z) to cylindrical coordinates of the form \displaystyle (r,\theta,z), the first and third terms are the most straightforward.

\displaystyle r=\sqrt{x^2+y^2}

\displaystyle z=z

Care should be taken, however, when calculating \displaystyle \theta. The formula for it is as follows: 

\displaystyle \theta=arctan(\frac{y}{x})

However, it is important to be mindful of the signs of both \displaystyle y and \displaystyle x, bearing in mind which quadrant the point lies; this will determine the value of \displaystyle \theta:

Quadrants

It is something to bear in mind when making a calculation using a calculator; negative \displaystyle y values by convention create a negative \displaystyle \theta, while negative \displaystyle x values lead to \displaystyle |\theta|>90^{\circ};\frac{\pi}{2}

For our coordinates \displaystyle (8,1,7)

\displaystyle \begin{align*}&r=\sqrt{(8)^2+(1)^2}=8.06\\&\theta=arctan(\frac{1}{8})=7.13^{\circ}\\&z=7\end{align*}

Example Question #121 : 3 Dimensional Space

A point in space is located, in Cartesian coordinates, at \displaystyle (3,4,7). What is the position of this point in cylindrical coordinates?

Possible Answers:

\displaystyle (7,126.87^{\circ},7)

\displaystyle (7,-53.13^{\circ},7)

\displaystyle (5,53.13^{\circ},7)

\displaystyle (7,53.13^{\circ},7)

\displaystyle (5,-126.87^{\circ},7)

Correct answer:

\displaystyle (5,53.13^{\circ},7)

Explanation:

When given Cartesian coordinates of the form \displaystyle (x,y,z) to cylindrical coordinates of the form \displaystyle (r,\theta,z), the first and third terms are the most straightforward.

\displaystyle r=\sqrt{x^2+y^2}

\displaystyle z=z

Care should be taken, however, when calculating \displaystyle \theta. The formula for it is as follows: 

\displaystyle \theta=arctan(\frac{y}{x})

However, it is important to be mindful of the signs of both \displaystyle y and \displaystyle x, bearing in mind which quadrant the point lies; this will determine the value of \displaystyle \theta:

Quadrants

It is something to bear in mind when making a calculation using a calculator; negative \displaystyle y values by convention create a negative \displaystyle \theta, while negative \displaystyle x values lead to \displaystyle |\theta|>90^{\circ};\frac{\pi}{2}

For our coordinates \displaystyle (3,4,7)

\displaystyle \begin{align*}&r=\sqrt{(3)^2+(4)^2}=5\\&\theta=arctan(\frac{4}{3})=53.13^{\circ}\\&z=7\end{align*}

Example Question #43 : Cylindrical Coordinates

A point in space is located, in Cartesian coordinates, at \displaystyle (-5,-7,5). What is the position of this point in cylindrical coordinates?

Possible Answers:

\displaystyle (8.6,54.46^{\circ},5)

\displaystyle (8.6,125.54^{\circ},5)

\displaystyle (-12,-125.54^{\circ},5)

\displaystyle (8.6,-125.54^{\circ},5)

\displaystyle (-12,54.46^{\circ},5)

Correct answer:

\displaystyle (8.6,-125.54^{\circ},5)

Explanation:

When given Cartesian coordinates of the form \displaystyle (x,y,z) to cylindrical coordinates of the form \displaystyle (r,\theta,z), the first and third terms are the most straightforward.

\displaystyle r=\sqrt{x^2+y^2}

\displaystyle z=z

Care should be taken, however, when calculating \displaystyle \theta. The formula for it is as follows: 

\displaystyle \theta=arctan(\frac{y}{x})

However, it is important to be mindful of the signs of both \displaystyle y and \displaystyle x, bearing in mind which quadrant the point lies; this will determine the value of \displaystyle \theta:

Quadrants

It is something to bear in mind when making a calculation using a calculator; negative \displaystyle y values by convention create a negative \displaystyle \theta, while negative \displaystyle x values lead to \displaystyle |\theta|>90^{\circ};\frac{\pi}{2}

For our coordinates \displaystyle (-5,-7,5)

\displaystyle \begin{align*}&r=\sqrt{(-5)^2+(-7)^2}=8.6\\&\theta=arctan(\frac{-7}{-5})=-125.54^{\circ}\\&z=5\end{align*}

Example Question #122 : 3 Dimensional Space

A point in space is located, in Cartesian coordinates, at \displaystyle (-8,4,1). What is the position of this point in cylindrical coordinates?

Possible Answers:

\displaystyle (-4,26.57^{\circ},1)

\displaystyle (8.94,-26.57^{\circ},1)

\displaystyle (8.94,-153.43^{\circ},1)

\displaystyle (8.94,153.43^{\circ},1)

\displaystyle (-4,153.43^{\circ},1)

Correct answer:

\displaystyle (8.94,153.43^{\circ},1)

Explanation:

When given Cartesian coordinates of the form \displaystyle (x,y,z) to cylindrical coordinates of the form \displaystyle (r,\theta,z), the first and third terms are the most straightforward.

\displaystyle r=\sqrt{x^2+y^2}

\displaystyle z=z

Care should be taken, however, when calculating \displaystyle \theta. The formula for it is as follows: 

\displaystyle \theta=arctan(\frac{y}{x})

However, it is important to be mindful of the signs of both \displaystyle y and \displaystyle x, bearing in mind which quadrant the point lies; this will determine the value of \displaystyle \theta:

Quadrants

It is something to bear in mind when making a calculation using a calculator; negative \displaystyle y values by convention create a negative \displaystyle \theta, while negative \displaystyle x values lead to \displaystyle |\theta|>90^{\circ};\frac{\pi}{2}

For our coordinates \displaystyle (-8,4,1)

\displaystyle \begin{align*}&r=\sqrt{(-8)^2+(4)^2}=8.94\\&\theta=arctan(\frac{4}{-8})=153.43^{\circ}\\&z=1\end{align*}

Example Question #41 : Cylindrical Coordinates

A point in space is located, in Cartesian coordinates, at \displaystyle (-4,-1,-4). What is the position of this point in cylindrical coordinates?

Possible Answers:

\displaystyle (-5,14.04^{\circ},-4)

\displaystyle (4.12,-165.96^{\circ},-4)

\displaystyle (-5,-165.96^{\circ},-4)

\displaystyle (4.12,14.04^{\circ},-4)

\displaystyle (4.12,165.96^{\circ},-4)

Correct answer:

\displaystyle (4.12,-165.96^{\circ},-4)

Explanation:

When given Cartesian coordinates of the form \displaystyle (x,y,z) to cylindrical coordinates of the form \displaystyle (r,\theta,z), the first and third terms are the most straightforward.

\displaystyle r=\sqrt{x^2+y^2}

\displaystyle z=z

Care should be taken, however, when calculating \displaystyle \theta. The formula for it is as follows: 

\displaystyle \theta=arctan(\frac{y}{x})

However, it is important to be mindful of the signs of both \displaystyle y and \displaystyle x, bearing in mind which quadrant the point lies; this will determine the value of \displaystyle \theta:

Quadrants

It is something to bear in mind when making a calculation using a calculator; negative \displaystyle y values by convention create a negative \displaystyle \theta, while negative \displaystyle x values lead to \displaystyle |\theta|>90^{\circ};\frac{\pi}{2}

For our coordinates \displaystyle (-4,-1,-4)

\displaystyle \begin{align*}&r=\sqrt{(-4)^2+(-1)^2}=4.12\\&\theta=arctan(\frac{-1}{-4})=-165.96^{\circ}\\&z=-4\end{align*}

Example Question #42 : Cylindrical Coordinates

A point in space is located, in Cartesian coordinates, at \displaystyle (3,6,-5). What is the position of this point in cylindrical coordinates?

Possible Answers:

\displaystyle (9,63.43^{\circ},-5)

\displaystyle (9,116.57^{\circ},-5)

\displaystyle (6.71,-116.57^{\circ},-5)

\displaystyle (6.71,116.57^{\circ},-5)

\displaystyle (6.71,63.43^{\circ},-5)

Correct answer:

\displaystyle (6.71,63.43^{\circ},-5)

Explanation:

When given Cartesian coordinates of the form \displaystyle (x,y,z) to cylindrical coordinates of the form \displaystyle (r,\theta,z), the first and third terms are the most straightforward.

\displaystyle r=\sqrt{x^2+y^2}

\displaystyle z=z

Care should be taken, however, when calculating \displaystyle \theta. The formula for it is as follows: 

\displaystyle \theta=arctan(\frac{y}{x})

However, it is important to be mindful of the signs of both \displaystyle y and \displaystyle x, bearing in mind which quadrant the point lies; this will determine the value of \displaystyle \theta:

Quadrants

It is something to bear in mind when making a calculation using a calculator; negative \displaystyle y values by convention create a negative \displaystyle \theta, while negative \displaystyle x values lead to \displaystyle |\theta|>90^{\circ};\frac{\pi}{2}

For our coordinates \displaystyle (3,6,-5)

\displaystyle \begin{align*}&r=\sqrt{(3)^2+(6)^2}=6.71\\&\theta=arctan(\frac{6}{3})=63.43^{\circ}\\&z=-5\end{align*}

Example Question #42 : Cylindrical Coordinates

A point in space is located, in Cartesian coordinates, at \displaystyle (-6,-6,-4). What is the position of this point in cylindrical coordinates?

Possible Answers:

\displaystyle (8.49,45^{\circ},-4)

\displaystyle (12,135^{\circ},-4)

\displaystyle (8.49,-45^{\circ},-4)

\displaystyle (12,45^{\circ},-4)

\displaystyle (8.49,-135^{\circ},-4)

Correct answer:

\displaystyle (8.49,-135^{\circ},-4)

Explanation:

When given Cartesian coordinates of the form \displaystyle (x,y,z) to cylindrical coordinates of the form \displaystyle (r,\theta,z), the first and third terms are the most straightforward.

\displaystyle r=\sqrt{x^2+y^2}

\displaystyle z=z

Care should be taken, however, when calculating \displaystyle \theta. The formula for it is as follows: 

\displaystyle \theta=arctan(\frac{y}{x})

However, it is important to be mindful of the signs of both \displaystyle y and \displaystyle x, bearing in mind which quadrant the point lies; this will determine the value of \displaystyle \theta:

Quadrants

It is something to bear in mind when making a calculation using a calculator; negative \displaystyle y values by convention create a negative \displaystyle \theta, while negative \displaystyle x values lead to \displaystyle |\theta|>90^{\circ};\frac{\pi}{2}

For our coordinates \displaystyle (-6,-6,-4)

\displaystyle \begin{align*}&r=\sqrt{(-6)^2+(-6)^2}=8.49\\&\theta=arctan(\frac{-6}{-6})=-135^{\circ}\\&z=-4\end{align*}

Example Question #43 : Cylindrical Coordinates

A point in space is located, in Cartesian coordinates, at \displaystyle (9,-1,4). What is the position of this point in cylindrical coordinates?

Possible Answers:

\displaystyle (9.06,173.66^{\circ},4)

\displaystyle (8,-173.66^{\circ},4)

\displaystyle (9.06,-6.34^{\circ},4)

\displaystyle (8,173.66^{\circ},4)

\displaystyle (8,-6.34^{\circ},4)

Correct answer:

\displaystyle (9.06,-6.34^{\circ},4)

Explanation:

When given Cartesian coordinates of the form \displaystyle (x,y,z) to cylindrical coordinates of the form \displaystyle (r,\theta,z), the first and third terms are the most straightforward.

\displaystyle r=\sqrt{x^2+y^2}

\displaystyle z=z

Care should be taken, however, when calculating \displaystyle \theta. The formula for it is as follows: 

\displaystyle \theta=arctan(\frac{y}{x})

However, it is important to be mindful of the signs of both \displaystyle y and \displaystyle x, bearing in mind which quadrant the point lies; this will determine the value of \displaystyle \theta:

Quadrants

It is something to bear in mind when making a calculation using a calculator; negative \displaystyle y values by convention create a negative \displaystyle \theta, while negative \displaystyle x values lead to \displaystyle |\theta|>90^{\circ};\frac{\pi}{2}

For our coordinates \displaystyle (9,-1,4)

\displaystyle \begin{align*}&r=\sqrt{(9)^2+(-1)^2}=9.06\\&\theta=arctan(\frac{-1}{9})=-6.34^{\circ}\\&z=4\end{align*}

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