Calculus 2 : Graphing Polar Form

Study concepts, example questions & explanations for Calculus 2

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Example Questions

Example Question #11 : Graphing Polar Form

Describe the graph of   from .

Possible Answers:

vertical line at 

line passing through the origin and 

horizontal line at 

circle centered around the origin with a radius of 

Correct answer:

vertical line at 

Explanation:

Graphing polar equations is different that plotting cartesian equations. Instead of plotting an  coordinate, polar graphs consist of an  coordinate where  is the radial distance of a point from the origin and  is the angle above the x-axis.

Using the identity , we see the graph of  will have the same shape as the graph , or a vertical line at .

 Fig3

Example Question #12 : Graphing Polar Form

Describe the graph of   from .

Possible Answers:

line passing through the origin and

horizontal line at 

circle centered at the origin with a radius of 

vertical line at 

Correct answer:

horizontal line at 

Explanation:

Graphing polar equations is different that plotting cartesian equations. Instead of plotting an  coordinate, polar graphs consist of an  coordinate where  is the radial distance of a point from the origin and  is the angle above the x-axis.

Using the identity , we see the graph of  will have the same shape as the graph , or a horizontal line at .

Fig4

Example Question #13 : Graphing Polar Form

 Describe the graph of   from .

Possible Answers:

circle centered around  with a radius of 

line passing through the origin and 

circle centered around  with a radius of 

circle centered around  with a radius of 

Correct answer:

circle centered around  with a radius of 

Explanation:

Graphing polar equations is different that plotting cartesian equations.  Instead of plotting an  coordinate, polar graphs consist of an  coordinate where  is the radial distance of a point from the origin and  is the angle above the x-axis.

Substituting values of  (in radians) between  and  into our expression, we find values of r. We then plot each ordered pair, , using the  value as the radius and  as the angle.  We get the graph below, a circle centered around  with a radius of .

Fig5

Example Question #14 : Graphing Polar Form

Describe the graph of   from .

Possible Answers:

circle centered around  with a radius of 

circle centered around  with a radius of 

circle centered around  with a radius of 

circle centered around  with a radius of 

Correct answer:

circle centered around  with a radius of 

Explanation:

Graphing polar equations is different that plotting cartesian equations.  Instead of plotting an  coordinate, polar graphs consist of an  coordinate where  is the radial distance of a point from the origin and  is the angle above the x-axis.

Substituting values of  (in radians) between  and  into our expression, we find values of r. We then plot each ordered pair, , using the  value as the radius and  as the angle. We get the graph below, a circle centered around  with a radius of .

Fig6

Example Question #15 : Graphing Polar Form

Describe the graph of  from .

Possible Answers:

an upright cardioid 

a cardioid (heart shape) rotated  left

a cardioid (heart shape) rotated  right

an upside-down cardioid 

Correct answer:

a cardioid (heart shape) rotated  left

Explanation:

Graphing polar equations is different that plotting cartesian equations.  Instead of plotting an  coordinate, polar graphs consist of an  coordinate where  is the radial distance of a point from the origin and  is the angle above the x-axis.

From our equation, we know the shape of our graph will be a cardioid because our equation is in the form  where .  Our cardioid is symmetric about the x-axis because our equation includes the  function  The point of the cardioid is at the origin. The y-intercepts are at  and . The x-intercept is at .

We could also substitute values of  (in radians) between  and  into our expression, to find values of r. We then plot each ordered pair, , using the  value as the radius and  as the angle.  

We get the graph below, a cardioid (heart shape) rotated  left.

Fig7

 

 

Example Question #16 : Graphing Polar Form

Describe the graph of  from .

Possible Answers:

an upside down cardioid (heart shape)

an upright cardioid (heart shape)

a cardioid (heart shape) rotated  right

a cardioid (heart shape) rotated  left

Correct answer:

an upright cardioid (heart shape)

Explanation:

Graphing polar equations is different that plotting cartesian equations.  Instead of plotting an  coordinate, polar graphs consist of an  coordinate where  is the radial distance of a point from the origin and  is the angle above the x-axis.

 From our equation, we know the shape of our graph will be a cardioid because our equation is in the form  where .  Our cardioid is symmetric about the y-axis because our equation includes the  function. The point of the cardioid is at the origin.  The x-intercepts are at  and .  The y-intercept is at .

We could also substitute values of  (in radians) between  and  into our expression, to find values of r.  We then plot each ordered pair, , using the  value as the radius and  as the angle.  

We get the graph below, an upright cardioid (heart shape).

 

 Fig8

Example Question #111 : Polar

Describe the graph of  from .

Possible Answers:

A limacon without a loop rotated  right

An upright limacon without a loop

An upside-down limacon without a loop

A limacon without a loop rotated  left

Correct answer:

An upside-down limacon without a loop

Explanation:

Graphing polar equations is different that plotting cartesian equations.  Instead of plotting an  coordinate, polar graphs consist of an  coordinate where  is the radial distance of a point from the origin and  is the angle above the x-axis.

From our equation, we know the shape of our graph will be a limacon  because our equation is in the form  where . This limacon will have no loop because . Our limacon is symmetric about the y-axis because our equation includes the  function.  The x-intercepts are at  and .  The y-intercept is at .

We could also substitute values of  (in radians) between  and  into our expression, to find values of r. We then plot each ordered pair, , using the  value as the radius and  as the angle.  

We get the graph below, an upside-down limacon.

 

 Fig9

Example Question #11 : Graphing Polar Form

Describe the graph of  from .

Possible Answers:

A limacon without a loop rotated  left

A limacon without a loop rotated  right

An upright limacon without a loop

An upside down limacon without a loop

Correct answer:

A limacon without a loop rotated  right

Explanation:

Graphing polar equations is different that plotting cartesian equations.  Instead of plotting an  coordinate, polar graphs consist of an  coordinate where  is the radial distance of a point from the origin and  is the angle above the x-axis.

From our equation, we know the shape of our graph will be a limacon  because our equation is in the form  where .  This limacon will have no loop because . Our limacon is symmetric about the x-axis because our equation includes the  function. The y-intercepts are at  and .  The x-intercept is at .

We could also substitute values of  (in radians) between  and  into our expression, to find values of r.  We then plot each ordered pair, , using the  value as the radius and  as the angle.  

We get the graph below, an limacon turned  right.

 

 Fig10

Example Question #19 : Graphing Polar Form

Describe the graph of  from .

Possible Answers:

a limacon with a loop turned  left

a limacon with a loop turned  right

an upright limacon with a loop

an upside-down limacon with a loop

Correct answer:

a limacon with a loop turned  left

Explanation:

Graphing polar equations is different that plotting cartesian equations.  Instead of plotting an  coordinate, polar graphs consist of an  coordinate where  is the radial distance of a point from the origin and  is the angle above the x-axis.

From our equation, we know the shape of our graph will be a limacon because our equation is in the form  where . This limacon will have a loop because . The length of the loop is .  Our limacon is symmetric about the x-axis because our equation includes the  function. The y-intercepts are at  and .  The x-intercept is at .

We could also substitute values of  (in radians) between  and  into our expression, to find values of r. We then plot each ordered pair, , using the  value as the radius and  as the angle.  

We get the graph below, a limacon with a loop turned  left.

 

 Fig11

Example Question #20 : Graphing Polar Form

Describe the graph of   from .

Possible Answers:

a limacon with a loop turned  right

an upside-down limacon with a loop 

a limacon with a loop turned  left

an upright limacon with a loop 

Correct answer:

an upright limacon with a loop 

Explanation:

Graphing polar equations is different that plotting cartesian equations. Instead of plotting an  coordinate, polar graphs consist of an  coordinate where  is the radial distance of a point from the origin and  is the angle above the x-axis.

From our equation, we know the shape of our graph will be a limacon  because our equation is in the form  where .  This limacon will have a loop because . The length of the loop is .  Our limacon is symmetric about the y-axis because our equation includes the  function. The x-intercepts are at  and . The y-intercept is at .

We could also substitute values of  (in radians) between  and  into our expression, to find values of r. We then plot each ordered pair, , using the  value as the radius and  as the angle.  

We get the graph below, an upright limacon with a loop.

 Fig12

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