Circle equations (1 Viewer)
- Thread starter sedulous
- Start date
This is not really part of the General Maths course, so don't freak out guys.
Question 1:
Let r be the radius of the circle
So its equation is:
(x - r)2 + (y - r)2 = r2
Since the point (8,1) lies on the circumference, we have:
(8 - r)2 + (1 - r)2 = r2
64 - 16r + r2 + 1 - 2r + r2 = r2
65 - 18r + 2r2 = r2
r2 - 18r + 65 = 0
(r - 5)(r - 13) = 0
r = 5 or r = 13
The solution r = 5 would mean that the point is actually on the outer edge of the table.
The solution r = 13 means that the point is on the inside of the table, as shown in the diagram.
.: The radius of the table is 13 m.
Question 1:
Let r be the radius of the circle
So its equation is:
(x - r)2 + (y - r)2 = r2
Since the point (8,1) lies on the circumference, we have:
(8 - r)2 + (1 - r)2 = r2
64 - 16r + r2 + 1 - 2r + r2 = r2
65 - 18r + 2r2 = r2
r2 - 18r + 65 = 0
(r - 5)(r - 13) = 0
r = 5 or r = 13
The solution r = 5 would mean that the point is actually on the outer edge of the table.
The solution r = 13 means that the point is on the inside of the table, as shown in the diagram.
.: The radius of the table is 13 m.