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April 3rd, 2019, 01:07 AM  #1 
Newbie Joined: Apr 2019 From: South Africa Posts: 7 Thanks: 0  Problem involving a unit circle and two other coordinates
I have a little problem that I hope the community would be able to assist me with. I have a unit circle and inside that unit circle I have a point (A), outside that unit circle I have another point (B). Is there a way to find the coordinates of the point that intersects the radius of the unit circle and the line AB ? Am I making the problem clear enough ? 
April 3rd, 2019, 01:27 AM  #2 
Senior Member Joined: Feb 2016 From: Australia Posts: 1,826 Thanks: 646 Math Focus: Yet to find out. 
If by intersects the radius you mean intersects the circle, then yes, you have all the information you need.

April 3rd, 2019, 02:31 AM  #3 
Newbie Joined: Apr 2019 From: South Africa Posts: 7 Thanks: 0 
Awesome any ideas as to any online resources that I can use to figure it out ? I am not a school student and need to figure this out for a little "Project" Thanks... 
April 3rd, 2019, 04:31 AM  #4 
Newbie Joined: Apr 2019 From: South Africa Posts: 7 Thanks: 0 
My math skills are not very good and I would really appreciate the assistance, how would I even google such a problem ? Thanks 
April 3rd, 2019, 05:31 AM  #5  
Math Team Joined: Jul 2011 From: Texas Posts: 2,949 Thanks: 1555  Quote:
 
April 3rd, 2019, 06:00 AM  #6 
Newbie Joined: Apr 2019 From: South Africa Posts: 7 Thanks: 0 
Let me rephrase what I want to do.. I have a circle and a line starting in the circle, radius 1, which ends outside the circle. I want to know what formulas I would use to determine the x and y coordinate of intersection point between circle radius 1 and the line. For example. Point A and the center of my circle, coordinate 0,0 are both the same. Point B is 2 units away at coordinate 0,2. 0,1 is my intersection point. Thankyou for your time.. 
April 3rd, 2019, 06:06 AM  #7  
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,946 Thanks: 1137 Math Focus: Elementary mathematics and beyond  Quote:
Perhaps it's not clear to me exactly what you mean.  
April 3rd, 2019, 06:24 AM  #8 
Newbie Joined: Apr 2019 From: South Africa Posts: 7 Thanks: 0 
Ok allow me to rephrase then... I am only interested in the outer most edge of the circle where the radius is 1 
April 3rd, 2019, 06:37 AM  #9 
Math Team Joined: Jul 2011 From: Texas Posts: 2,949 Thanks: 1555 
Since A is at the origin and the unit circle is also,then the point of intersection for that segment AB and the circle would be $(x,y) = (\cos{\theta},\sin{\theta})$ where $\cos{\theta} = \dfrac{x_B}{\sqrt{x_B^2 + y_B^2}}$ and $\sin{\theta} = \dfrac{y_B}{\sqrt{x_B^2 + y_B^2}}$ 
April 3rd, 2019, 12:18 PM  #10 
Newbie Joined: Apr 2019 From: South Africa Posts: 7 Thanks: 0 
What if A was at any location within the circle of radius 1 ? Sorry for asking another question... 

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circle, coordinates, involving, problem, unit 
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