Equation of a Circle
Below is an activity with 3 circles and their equations. Look at the size, position and equation of the green circle. Use the constant controller to increase the value of r.
What do you think r stands for, and how does it effect the equation of the circle?
Now look at the size, position and equation of the blue circle. Select the centre of the circle and drag it around the page.
How does the centre of the circle effect the equation?
Now look at the size, position and equation of the red circle. Using what you have learnt, what do you think the equation of the red circle is?
Select the black rectangle, and drag it to the right to reveal the equation.
Drag the centre and the other highlighted point of the red circle around to produce the following equations:
This activity is great for students to play around with when first introducing them to the equation of a circle. From here you might want to go on to look at why it is the case.
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