Solving Cartesian Equation: r= 9 cosθ

  • Thread starter Thread starter knv
  • Start date Start date
  • Tags Tags
    Cartesian
Click For Summary
SUMMARY

The Cartesian equation for the polar curve r = 9 cosθ is x² + y² = 9x. The conversion process involves using the relationships rcosθ = x and cosθ = x/r. Initially, the user derived (x - 9/2)² + y² = (9/2)², which was incorrect for the online homework submission due to formatting issues. The correct form simplifies to x² + y² = 9x, which aligns with the expected answer.

PREREQUISITES
  • Understanding of polar coordinates and their conversion to Cartesian coordinates.
  • Familiarity with trigonometric identities, particularly rcosθ and cosθ.
  • Basic algebra skills for manipulating equations.
  • Experience with online homework systems and their formatting requirements.
NEXT STEPS
  • Study the conversion methods between polar and Cartesian coordinates.
  • Learn about the implications of equation formatting in online homework systems.
  • Explore additional examples of polar curves and their Cartesian equivalents.
  • Practice solving polar equations using software tools like GeoGebra or Desmos.
USEFUL FOR

Students studying mathematics, particularly those focusing on calculus and coordinate geometry, as well as educators looking to enhance their teaching methods for polar and Cartesian equations.

knv
Messages
17
Reaction score
0
1. Find a Cartesian equation to represent the curve r = 9 cosθ



2. I know that rcosθ= x and cos θ= x/r



3. I got (x-9/2)^2 +y^2 = (9/2)^2 but its coming up wrong when I put it into our online homework. Can anyone help me?
 
Physics news on Phys.org
hi knv! :smile:

(try using the X2 button just above the Reply box :wink:)
knv said:
1. Find a Cartesian equation to represent the curve r = 9 cosθ
I got (x-9/2)2 +y2 = (9/2)^2

how?? :confused:

anyway, just multiply by r …

r2 = 9rcosθ :smile:
 
knv said:
1. Find a Cartesian equation to represent the curve r = 9 cosθ



2. I know that rcosθ= x and cos θ= x/r



3. I got (x-9/2)^2 +y^2 = (9/2)^2 but its coming up wrong when I put it into our online homework. Can anyone help me?

Your result looks correct to me. It probably has something to do with how you "simplify" it before you type in the answer. Maybe something simple like writing the right side as 81/4?
 
the answer was more simple than I thought.

x2+y2=9x


Thanks!
 
knv said:
the answer was more simple than I thought.

x2+y2=9x


Thanks!

So your original answer was correct, just not in the form the software wanted.
 
yes. I always get things wrong just because its not in the form the software wanted. Miss when we could turn homework in on paper haha
 

Similar threads

  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
Replies
3
Views
1K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
Replies
1
Views
2K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 4 ·
Replies
4
Views
2K