# Circles!

• Jul 16th 2009, 06:12 PM
Pwntzyou
Circles!
http://img35.imageshack.us/img35/56/mathqyr.jpg

The above picture is a visualization of my problem (Programming, yay!).

What is labeled on the picture is what I know.

How would I be able to pick a point on the circle (the blue part) and solve for the coordinates of the point.

It has been awhile T.T
• Jul 16th 2009, 07:55 PM
VonNemo19
Can you use angles? if so, the arc formula or the law of cosines ought to do it. If not, I don't know what to tell you.
• Jul 16th 2009, 08:00 PM
AlephZero
Well the equation for a circle is $x^2+y^2=r^2.$ In your problem, none of these values x, y, or r are "known." So it's difficult to give you any kind of an answer without having some known values; particularly the location of the center of the large circle, as well as its radius. Without these, the problem makes little sense, so far as I can tell.
• Jul 16th 2009, 08:06 PM
VonNemo19
Quote:

Originally Posted by AlephZero
Without these, the problem makes little sense, so far as I can tell.

Well, if we define the circle as being in stanrd position, we can apply some trig to find the coordinates in question. But, we do need an angle. Or perhaps one of the members of the ordered pair.
• Jul 16th 2009, 08:39 PM
Pwntzyou
Quote:

Originally Posted by VonNemo19
Well, if we define the circle as being in stanrd position, we can apply some trig to find the coordinates in question. But, we do need an angle. Or perhaps one of the members of the ordered pair.

This is more or less a not very specific problem, but knowing that I do have the location of the center of the circle, and the radius, would it be possible.

Edit:

I also know the radians / degrees of the direction of the two points.
• Jul 16th 2009, 08:50 PM
AlephZero
Quote:

Originally Posted by Pwntzyou
This is more or less a not very specific problem, but knowing that I do have the location of the center of the circle, and the radius, would it be possible.

Yes, would be the simple answer. All points (x, y) will satisfy $x^2+y^2=r^2,$ and you will want to limit your choices of x and y so that they lie along the blue arc, which will depend on the angle you're sweeping out with your red lines.