Calculus 3 : Calculus 3

Study concepts, example questions & explanations for Calculus 3

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Example Questions

Example Question #69 : Cylindrical Coordinates

A point in space is located, in Cartesian coordinates, at \(\displaystyle (12,-5,31)\). What is the position of this point in cylindrical coordinates?

Possible Answers:

\(\displaystyle (13,-22.62^{\circ},31)\)

\(\displaystyle (13,157.38^{\circ},31)\)

\(\displaystyle (13,22.62^{\circ},31)\)

\(\displaystyle (7,157.38^{\circ},31)\)

\(\displaystyle (7,-22.62^{\circ},31)\)

Correct answer:

\(\displaystyle (13,-22.62^{\circ},31)\)

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 \(\displaystyle (12,-5,31)\)

 \(\displaystyle \begin{align*}&r=\sqrt{(12)^2+(-5)^2}=13\\&\theta=arctan(\frac{-5}{12})=-22.62^{\circ}\\&z=31\end{align*}\)

 

Example Question #70 : Cylindrical Coordinates

A point in space is located, in Cartesian coordinates, at \(\displaystyle (-24,10,32)\). What is the position of this point in cylindrical coordinates?

Possible Answers:

\(\displaystyle (26,22.62^{\circ},32)\)

\(\displaystyle (26,-22.62^{\circ},32)\)

\(\displaystyle (26,157.38^{\circ},32)\)

\(\displaystyle (14,22.62^{\circ},32)\)

\(\displaystyle (14,157.38^{\circ},32)\)

Correct answer:

\(\displaystyle (26,157.38^{\circ},32)\)

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 \(\displaystyle (-24,10,32)\)

 \(\displaystyle \begin{align*}&r=\sqrt{(-24)^2+(10)^2}=26\\&\theta=arctan(\frac{10}{-24})=157.38^{\circ}\\&z=32\end{align*}\)

Example Question #1821 : Calculus 3

A point in space is located, in Cartesian coordinates, at \(\displaystyle (20,14,25)\). What is the position of this point in cylindrical coordinates?

Possible Answers:

\(\displaystyle (24.41,34.99^{\circ},25)\)

\(\displaystyle (34,-145.01^{\circ},25)\)

\(\displaystyle (34,34.99^{\circ},25)\)

\(\displaystyle (34,145.01^{\circ},25)\)

\(\displaystyle (24.41,145.01^{\circ},25)\)

Correct answer:

\(\displaystyle (24.41,34.99^{\circ},25)\)

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 \(\displaystyle (20,14,25)\)

 \(\displaystyle \begin{align*}&r=\sqrt{(20)^2+(14)^2}=24.41\\&\theta=arctan(\frac{14}{20})=34.99^{\circ}\\&z=25\end{align*}\)

 

Example Question #71 : Cylindrical Coordinates

A point in space is located, in Cartesian coordinates, at \(\displaystyle (-9,12,15)\). What is the position of this point in cylindrical coordinates?

Possible Answers:

\(\displaystyle (15,-53.13^{\circ},15)\)

\(\displaystyle (15,53.13^{\circ},15)\)

\(\displaystyle (3,126.87^{\circ},15)\)

\(\displaystyle (15,126.87^{\circ},15)\)

\(\displaystyle (3,-53.13^{\circ},15)\)

Correct answer:

\(\displaystyle (15,126.87^{\circ},15)\)

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 \(\displaystyle (-9,12,15)\)

 \(\displaystyle \begin{align*}&r=\sqrt{(-9)^2+(12)^2}=15\\&\theta=arctan(\frac{12}{-9})=126.87^{\circ}\\&z=15\end{align*}\)

 

Example Question #73 : Cylindrical Coordinates

A point in space is located, in Cartesian coordinates, at \(\displaystyle (36,-160,18)\). What is the position of this point in cylindrical coordinates?

Possible Answers:

\(\displaystyle (164,102.68^{\circ},18)\)

\(\displaystyle (164,-77.32^{\circ},18)\)

\(\displaystyle (124,102.68^{\circ},18)\)

\(\displaystyle (124,-77.32^{\circ},18)\)

\(\displaystyle (124,77.32^{\circ},18)\)

Correct answer:

\(\displaystyle (164,-77.32^{\circ},18)\)

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 \(\displaystyle (36,-160,18)\)

 \(\displaystyle \begin{align*}&r=\sqrt{(36)^2+(-160)^2}=164\\&\theta=arctan(\frac{-160}{36})=-77.32^{\circ}\\&z=18\end{align*}\)

 

Example Question #74 : Cylindrical Coordinates

A point in space is located, in Cartesian coordinates, at \(\displaystyle (-1.5,-2,10)\). What is the position of this point in cylindrical coordinates?

Possible Answers:

\(\displaystyle (2.5,53.13^{\circ},10)\)

\(\displaystyle (2.5,-126.87^{\circ},10)\)

\(\displaystyle (3.5,-126.87^{\circ},10)\)

\(\displaystyle (2.5,126.87^{\circ},10)\)

\(\displaystyle (3.5,53.13^{\circ},10)\)

Correct answer:

\(\displaystyle (2.5,-126.87^{\circ},10)\)

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 \(\displaystyle (-1.5,-2,10)\)

 \(\displaystyle \begin{align*}&r=\sqrt{(-1.5)^2+(-2)^2}=2.5\\&\theta=arctan(\frac{-2}{-1.5})=-126.87^{\circ}\\&z=10\end{align*}\)

 

Example Question #72 : Cylindrical Coordinates

A point in space is located, in Cartesian coordinates, at \(\displaystyle (-50,120,100)\). What is the position of this point in cylindrical coordinates?

Possible Answers:

\(\displaystyle (70,112.62^{\circ},100)\)

\(\displaystyle (130,-67.38^{\circ},100)\)

\(\displaystyle (70,67.38^{\circ},100)\)

\(\displaystyle (70,-67.38^{\circ},100)\)

\(\displaystyle (130,112.62^{\circ},100)\)

Correct answer:

\(\displaystyle (130,112.62^{\circ},100)\)

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 \(\displaystyle (-50,120,100)\)

 \(\displaystyle \begin{align*}&r=\sqrt{(-50)^2+(120)^2}=130\\&\theta=arctan(\frac{120}{-50})=112.62^{\circ}\\&z=100\end{align*}\)

 

Example Question #73 : Cylindrical Coordinates

A point in space is located, in Cartesian coordinates, at \(\displaystyle (5,-25,-6)\). What is the position of this point in cylindrical coordinates?

Possible Answers:

\(\displaystyle (25.5,78.69^{\circ},-6)\)

\(\displaystyle (20,101.31^{\circ},-6)\)

\(\displaystyle (20,-78.69^{\circ},-6)\)

\(\displaystyle (25.5,101.31^{\circ},-6)\)

\(\displaystyle (25.5,-78.69^{\circ},-6)\)

Correct answer:

\(\displaystyle (25.5,-78.69^{\circ},-6)\)

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 \(\displaystyle (5,-25,-6)\)

 \(\displaystyle \begin{align*}&r=\sqrt{(5)^2+(-25)^2}=25.5\\&\theta=arctan(\frac{-25}{5})=-78.69^{\circ}\\&z=-6\end{align*}\)

 

Example Question #74 : Cylindrical Coordinates

A point in space is located, in Cartesian coordinates, at \(\displaystyle (1,-1.707,6)\). What is the position of this point in cylindrical coordinates?

Possible Answers:

\(\displaystyle (0.71,120.36^{\circ},6)\)

\(\displaystyle (0.71,-120.36^{\circ},6)\)

\(\displaystyle (1.98,-59.64^{\circ},6)\)

\(\displaystyle (0.71,-59.64^{\circ},6)\)

\(\displaystyle (1.98,120.36^{\circ},6)\)

Correct answer:

\(\displaystyle (1.98,-59.64^{\circ},6)\)

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 \(\displaystyle (1,-1.707,6)\)

 \(\displaystyle \begin{align*}&r=\sqrt{(1)^2+(-1.71)^2}=1.98\\&\theta=arctan(\frac{-1.71}{1})=-59.64^{\circ}\\&z=6\end{align*}\)

 

Example Question #75 : Cylindrical Coordinates

A point in space is located, in Cartesian coordinates, at \(\displaystyle (7,21,22)\). What is the position of this point in cylindrical coordinates?

Possible Answers:

\(\displaystyle (22.14,108.43^{\circ},22)\)

\(\displaystyle (28,108.43^{\circ},22)\)

\(\displaystyle (28,71.57^{\circ},22)\)

\(\displaystyle (22.14,71.57^{\circ},22)\)

\(\displaystyle (22.14,-71.57^{\circ},22)\)

Correct answer:

\(\displaystyle (22.14,71.57^{\circ},22)\)

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 \(\displaystyle (7,21,22)\)

 \(\displaystyle \begin{align*}&r=\sqrt{(7)^2+(21)^2}=22.14\\&\theta=arctan(\frac{21}{7})=71.57^{\circ}\\&z=22\end{align*}\)

 

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