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Equation of the Unit Circle Centered at the Origin

Definition

The unit circle centered at the origin is the locus of points whose distance from the origin is equal to 1 unit.

1. Graph

Move the center of the circle and adjust the radius until the graph shows the unit circle centered at the origin.

2. Distance from the Origin

Now that you have the unit circle centered at the origin, how far is the green point from the origin? Explain.

3. Equation of Unit Circle

Let the coordinates of the green point be represented by the coordinates (x,y). Write an equation that says that the distance between (x,y) and the origin is equal to your answer to Question 2. Then square both sides of your equation.