SRL Archive - Mathematics

Ive got points
A(-2,3)
B(4,2)
C(2,-3)

How do i find the center point of a circle using those points the points are the circumference the circle

System of equations, basically. :)

http://mathforum.org/library/drmath/view/55239.html

From: Ogre
System of equations, basically. :)

http://mathforum.org/library/drmath/view/55239.html

Nooooooooo, don't do system of equations! That's almost a no-brainer approach!

Take any two points, and find the equation of the line perpendicular to the chord that joins those two points and passes through the midpoint of the two points.

Take any other two points, and do the same.

Then find the point of intersection of the two lines which you've derived the equations for.

What do I mean?

Line perpendicular to AB that passes through midpoint of A and B:
Gradient = 6, Point = (1, 2.5)

y - 2.5 = 6(x - 1), 6 = 6x - 3.5

Line perpendicular to AC that passes through midpoint of A and C:
Gradient = 2/3, Point = (0, 0)

y = 2x/3

Solving two lines simultaneously:

6x - 3.5 = 2x/3, 18x - 10.5 = 2x, 16x = 10.5…and solve.

Of course, I may have made a mistake somewhere…but the method is correct.

Hi Santy!


Here's a picture aid of what Santa was talking about.