Coordinate geometry of circles

What you'll learn

1. 1

   A circle in coordinate geometry is just a set of points that are all the same distance from one fixed point — the centre.

2. 2

   Here's a circle centred at (0,0) with radius 5. Every point on the circle is exactly 5 units from the centre.

3. 3

   Find the equation of a circle with centre (2, -3) and radius 4.

4. 4

   Drag the centre and radius to make a circle that passes through the point (6, 1).

5. 5

   What is the equation of a circle with centre (0,0) and radius 3?

6. 6

   Does the point (5, -1) lie on the circle (x - 3)² + (y + 1)² = 8?

7. 7

   Which point lies on the circle x² + y² = 25?