### Home > APCALC > Chapter 6 > Lesson 6.4.2 > Problem 6-141

6-141.

The last remaining basic equation without a derivative is the equation of a circle, , where

*r*is a constant. What is

Recall that a circle is NOT a function.

Before differentiating, you could solve for *y* and get

Then find the derivative of each piece separately, or.....

You could use implicit differentiation!

Implicit differentiation: