Have a look at the teddy bear – can you identify all the equations from this list?
This problem comes from the excellent Underground Maths site.
You can view the Teddy Bear on Desmos by selecting the image above.
Note that on Desmos you can choose to display or hide a graph.
As with all problems on the site you can see the question and a very full solution with all reasoning explained.
For further notes on the equation of a circle, check these Helm Project notes and exercises on the circle.