Convert equation 8x=8y to polar form

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Discussion Overview

The discussion revolves around converting the Cartesian equation 8x=8y into polar form. Participants explore various approaches to the conversion, including the use of trigonometric identities and the implications of dividing by r.

Discussion Character

  • Homework-related, Mathematical reasoning, Technical explanation

Main Points Raised

  • One participant initially attempts to convert the equation by substituting x and y with polar coordinates, leading to the equation 8*r*cos(theta)=8*r*sin(theta), which they find incorrect.
  • Another participant suggests that dividing by 8 simplifies the equation to r*cos(theta)=r*sin(theta), but they also encounter difficulties.
  • A participant notes that dividing by r (assuming it is not zero) leads to the equation cos(theta) = sin(theta), indicating multiple possible values for theta.
  • Further exploration leads to the equation tan(theta) = 1, prompting questions about the implications for theta.
  • Participants discuss the general form of polar equations corresponding to Cartesian lines, suggesting that a line of the form y=ax translates to tan(theta)=a.
  • There is mention of the need for a polar equation involving both r and theta for lines not passing through the origin.
  • One participant expresses frustration that their attempts to input the derived equations into a system have not been successful.
  • Another participant suggests a specific form for theta, but it also does not yield the expected results.
  • Finally, a recommendation is made to consult the professor for clarification on the assignment requirements.

Areas of Agreement / Disagreement

Participants generally agree on the steps to convert the equation and the implications of dividing by r, but there is no consensus on the final form of the polar equation or the correct input for the assignment.

Contextual Notes

Participants express uncertainty regarding the requirements for the polar equation and the system's response to their inputs. There is also a reliance on assumptions about the values of r and theta.

Elissa89
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Convert the equation to polar form

8x=8y

I thought it would be

8*r*cos(theta)=8*r*sin(theta)

Said it was incorrect

then I thought I needed to divide by 8 to remove it, giving me:

r*cos(theta)=r*sin(theta)

But that was also incorrect and now I am stuck
 
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Elissa89 said:
Convert the equation to polar form

8x=8y

I thought it would be

8*r*cos(theta)=8*r*sin(theta)

Said it was incorrect

then I thought I needed to divide by 8 to remove it, giving me:

r*cos(theta)=r*sin(theta)

But that was also incorrect and now I am stuck
Either there's a typo somewhere or this is too simple a problem.

Your difficulty is that you stopped too soon. You can also divide by r (assuming that it's not zero). Thus you have the equation: [math]cos( \theta ) = sin( \theta )[/math]. There are several possible values for [math]\theta[/math].

-Dan
 
topsquark said:
Either there's a typo somewhere or this is too simple a problem.

Your difficulty is that you stopped too soon. You can also divide by r (assuming that it's not zero). Thus you have the equation: [math]cos( \theta ) = sin( \theta )[/math]. There are several possible values for [math]\theta[/math].

-Dan
Nope, no typo. I also tried cos(theta)=sin(theta). Then I thought I need to get the r alone and I got r=r*tan(theta)
 
Elissa89 said:
Nope, no typo. I also tried cos(theta)=sin(theta). Then I thought I need to get the r alone and I got r=r*tan(theta)

If you divided through by \(r\), you have:

$$\tan(\theta)=1$$

What does this imply for \(\theta\)?
 
MarkFL said:
If you divided through by \(r\), you have:

$$\tan(\theta)=1$$

What does this imply for \(\theta\)?

I tried inputting pi/4 and 5pi/4, but it doesn't want an answer, it wants the question converted to a polar equation.
 
Elissa89 said:
I tried inputting pi/4 and 5pi/4, but it doesn't want an answer, it wants the question converted to a polar equation.

Any Cartesian line of the form:

$$y=ax$$

will correspond to a polar equation of the form:

$$\tan(\theta)=a$$

or:

$$\theta=\arctan(a)+k\pi$$

Only a line not passing through the origin will have a polar equation involving both \(r\) and \(\theta\).

Did you try inputting:

$$\tan(\theta)=1$$ ?
 
MarkFL said:
Any Cartesian line of the form:

$$y=ax$$

will correspond to a polar equation of the form:

$$\tan(\theta)=a$$

or:

$$\theta=\arctan(a)+k\pi$$

Only a line not passing through the origin will have a polar equation involving both \(r\) and \(\theta\).

Did you try inputting:

$$\tan(\theta)=1$$ ?

Yes, it didn't take it
 
Elissa89 said:
Yes, it didn't take it

Perhaps it wants:

$$\theta=\frac{\pi}{4}(4k+1)$$
 
MarkFL said:
Perhaps it wants:

$$\theta=\frac{\pi}{4}(4k+1)$$

It still didn't take it
 
  • #10
Elissa89 said:
It still didn't take it

At this point, I would recommend you speak to the professor, and let him/her know what you've done.
 
  • #11
MarkFL said:
At this point, I would recommend you speak to the professor, and let him/her know what you've done.

Yeah I shot him a message, I just hope he gets back to me in time, assignment is due tonight at midnight
 

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