Circle (Quadratic Relations)

Shift-drag: Hold down the shift key, then drag the described object.
Control-drag: Hold down the control key, then drag the described object.
Control-shift-drag: Hold down both the control key and the shift key, then drag the described object.

The sliders change the parameters h, k and r in the quadratic relation ( x − h )² + ( y − k )² = r².

Drag a slider to change the value of a parameter.
The <LEFT> and <RIGHT> arrow keys can be used to change the selected parameter [light blue].
The <UP> and <DOWN> arrow keys can be used to increase or decrease the selected parameter. (Use this feature for fine adjustments.)
If the arrow keys don't respond, click the cursor in the applet frame then try again.
Drag a parameter scale to "move" it. (I.e., change the range but maintain the scale "length".)
Drag towards or away from a parameter thumb to "re-scale" the scale.
Select the corresponding parameter button to enter a value for a parameter.

Drag the centre of the circle to move the circle in the coordinate system.
Drag a location along the circle to change the radius of the circle.
Click and drag any other location to see the coordinates of the cursor and locations along the circle.
Hold <SHIFT> and click and drag in the graph area to move the entire coordinate system.
Hold <CONTROL> and click and drag in the graph area towards or away from the origin to change the x and y axis scale.