1. Can the equation of a circle be differentiated?
Yes, by using implicit differentiation.
2. Should all implicit relations and functions be differentiated implicitly?
Not necessarily, if it is easy to re-arrange the relation first, the function should be made explicit and then differentiated "normally" .
3. Why is the term relation used and not function?
Because many implicit relations, such as circles, seldom fulfil the condition of a function i.e. One x-value gives just one y-value.
