Equation of a circle / polar coordinates

[Marioqwe]

I was looking at the equation of a circle in polar coordinates on wikipedia,

http://en.wikipedia.org/wiki/Polar_coordinate_system

and I understand that a is the radius of the circle, and that (r0, phi) is the center of the circle. But I don't see what the r and theta refer to :(.

 

[eumyang]

... I understand that a is the radius of the circle, and that (r0, phi) is the center of the circle. But I don't see what the r and theta refer to :(.

r and θ are just the variables in the equation.

Just like in rectangular coordinates, given a center (h, k) and radius r,
(x - h)² + (y - k)² = r²
is the equation of the circle, and x and y are the variables.

Or am I misunderstanding your question?

 

[Marioqwe]

So do they just represent a point inside the circle?

 

[eumyang]

So do they just represent a point inside the circle?

No, they represent a set of points that lie on the circle, not inside.

 

[Marioqwe]

What do you mean by [[/B]on[/B]? And by the way; sorry for giving you a hard time. English is not my first language.

 

[eumyang]

See attached picture. The red point is on the circle, while the blue point is inside the circle.