### E3 (adv) - write the equations of circles and ellipses in transformational form and as mapping rules to visualize and sketch graphs.

Lindsay

**Definitions:**

**Circle:** a single, closed curved line

**Ellipse:** a single, closed curved line that has one axis longer than the other (x-axis or y-axis) *Example below has a longer y-axis*

**Writing an equation for a circle:** To write an equation for a circle, it first needs to be put on a graph. Let's make it easy and have the centre of the circle at the origin of the graph (0,0).

The equation of a circle looks like this: **[1/r (x-h)]^2 + [1/r (y-k)]^2 **This is called **Transformational Form. **The r stands for Radius, h is the horizontal translation and k is the vertical translation.

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