The graph of a circle with centre (0, 0) and radius r is given by the equation:
Sketching Circles
The basic circle
If the equation is in the form x2 + y2 = r2 the following method should be used:
Sketch the graph of x2 + y2 = 25 Sketch the graph of x2 + y2 = 8 Radius = √25
Centre is (0, 0)Radius = √ 8 = 2.8 (to 2 sig.fig.)
Centre is (0, 0)
The centre is not the origin
In a similar manner to parabolas and cubics the basic circle can be transformed.
The most common transformation is when the centre of the circle is not the origin.
The graph of a circle with centre (a, b) and radius r is given by the equation:
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Example Sketch the graph of (x − 2)2 + (y + 3)2 = 9
Radius = √ 9 = 3 Centre is (2, -3) |
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