## Pages

### Interactive: Fermat's Theorem

Fermat's Theorem: If $$f$$ is a local maximum or minimum at $$c$$, and if $$f'(c)$$ exists, then $$f'(c)=0$$.

Critical Number: A number $$c$$ in the domain of $$f$$ such that either $$f'(c)=0$$ or $$f'(c)$$ does not exist.

Instructions: With the mouse, move point P along the function and you will see it's derivative traced in green. Here c and d are the critical numbers for the function graphed in blue. Refresh browser to start over.