Circle Equation: Center (0,0)

For the questions below, be sure to zoom out if you need to!

1.

Suppose P(x,y) = any point that lies on a circle with center (0,0) and radius 5. Use what you've observed to write an equation that expresses the relationship among x, y, and r.

2.

What is the equation of a circle with center (0,0) and radius r = 9?

3.

Suppose another circle has center (0,0). Suppose this circle also passes through the point (12, -5). Write the equation of this circle.

4. FINAL QUESTION:

Suppose P(x,y) = any point that lies on a circle with center (0,0) and radius r, where r > 0. Use what you've observed to write an equation that expresses the relationship among x, y, and r.

Quick (Silent) Demo