Include an explanation (answer)

A merry-go round, or carousel, or other similar circular carnival ride.

You could use the formula for a circle:

x^{2} + y^{2 }= r^{2}

Where r is the radius of the merry go round. For example, if the radius was 5 metres, r = 5. So:

x^{2} + y^{2} = 5^{2}